Proposal ID: 06_0001
Principal Investigator: William Reach (USRA/SOFIA)
Title: Supernova Remant-Molecular Cloud Interactions: What Types of Shock?
Abstract: When massive stars reach the end of their ability to remain stable with core nuclear fusion, they explode in supernovae that drive powerful shocks into their surroundings. Because massive stars form in and remain close to molecular clouds they often drive shocks into dense gas, which is now believed to be the origin of a significant fraction of galactic cosmic rays. The nature of the supernova-molecular cloud interaction is not well understood, though observations are gradually elucidating their nature. The range of interstellar densities, and the inclusion of circumstellar matter from the late-phase mass-loss of the stars before their explosions, leads to a wide range of possible appearances and outcomes. In particular, it is not even clear what speed or physical type of shocks are present: are they dense, magnetically-mediated shocks where H2 is not dissociated, or are they faster shocks that dissociate molecules and destroy some of the grains? We identified some of the most significant (in terms of cosmic ray production potential and infrared energy output) supernova-molecular cloud interactions for measurement of the line widths of key molecular shocks tracers: H2, [OI], and CO. The presence of gas at speeds 100 km/s or greater would indicate dissociative shocks, while speeds 30 km/s and slower retain most molecules. The shock velocity is a key ingredient in modeling the interaction between supernovae and molecular clouds including the potential for formation of cosmic rays.
Proposal ID: 06_0004
Principal Investigator: Charles E. Woodward (MN Institute for Astrophysics)
Title: Writanen and Friends
Abstract: Solar system formation is a process that simultaneously preserves and transforms ISM ices, organics, and dust grains into cometesimals, planetesimals and, ultimately, planets. Cometary dust contains remnants of both primordial material in the comet-formation zone as well as processed material transported from hotter regions closer to the Sun. They are primitive bodies, detritus from the epoch of planet formation. Why study comets? They can advance our understanding of both "How do circumstellar disks evolve and form planetary systems?" and "What are the initial stages, conditions and processes of solar system formation and the nature of the ISM that was incorporated?" We propose to observe (FORCAST/FPI+) 5 comets, including 46P/Writanen our JWST GTO target, to determine the coma grain properties and to characterize these bodies. Our SOFIA program addresses three questions: What information do the cometary grains provide us concerning the evolution of the early solar system? What are the fundamental differences between comets originating from different regions and times of the solar system? What is the connection between the properties of cometary grains derived from scattered light versus thermal emission?
Proposal ID: 06_0005
Principal Investigator: Eric Omelian (Space Science Institute)
Title: Studying the Silicate Dust Evolution in the Symbiotic Mira, R Aquarii
Abstract: R Aqr is a nearby, dusty symbiotic star, consisting of a mass losing Mira variable and a hot accreting White Dwarf (WD). It is surrounded by two extended shells caused by nova-like explosions that happened several hundred years ago, and contains a spectacular jet, which is fueled by the accretion flow onto the WD. R~Aqr is currently approaching the widely anticipated eclipse of the Mira by the WD, during which period the system will also go through periastron. The Mira in R~Aqr is oxygen-rich and its mid-IR spectrum shows the prominent silicate features at 10 and 18 mu-m on top of the thermal dust emission. These features are known to change in their shape both with the Mira phase and on the longer timescale of about 25 years (Monnier et al. 1998, 1999). We propose to obtain grism spectra across the silicate features, and photometry at several wavebands between 5 and 37 microns at two different Mira phases using FORCAST, and longer wavelength photometry in four bands between 58 and 214 microns using HAWC+. We will characterize the changes to the overall SED due to changes in the dust temperatures caused by the expected enhanced binary activity close to periastron, and also distinguish between changes to the silicate profile due to Mira phase, and any secular evolution correlated with the binary orbit. We will constrain the dust composition and size distribution as well as its temperature and density in the circumstellar envelope using 3D modeling of the emission. This proposal is the third in a series (following our successful Cycle 4 and 5 proposals) to monitor the mid- and far-IR emission from R Aqr through the upcoming eclipse and periastron passage.
Proposal ID: 06_0009
Principal Investigator: Imke de Pater (University of California – Berkeley)
Title: Jupiter's Tropospheric Dynamics from SOFIA Mapping of Temperature, Para-Hydrogen, and Aerosols
Abstract: We request time with FORCAST to observe Jupiter at mid-infrared wavelengths using 8-37 micron grism spectroscopy of the collisionally-induced H2-He continuum to derive the zonal mean tropospheric temperatures and para-H2 distribution. In addition, we request imaging in discrete filters between 5 and 37 micron to provide spatial context for the spectroscopy. This proposal is a follow-up of our successful observations in May 2014, where we confirmed the N-S polar asymmetry in the para-H2 fraction detected by Voyager 1, also during late summer in Jupiter's northern hemisphere. In spring 2018, during a world-wide campaign in support of the Juno mission, Jupiter is at/near southern summer solstice. This timing is ideal to assess seasonable variability on the planet.
Proposal ID: 06_0010
Principal Investigator: William Reach (SOFIA/USRA)
Title: Scale height of the Interstellar Medium in Edge-on Galaxies
Abstract: Active star formation in galaxies levitates material from the midplane. This process self-regulates the star-formation history of galaxies and is critical for understanding galaxy evolution. Spiral galaxies that are edge-on allow clear distinction of material that is levitated off the galaxies’ midplanes. We will measure the vertical distribution of [C II] and [O III] as tracers of the cold and hot interstellar medium. A set of 4 edge-on galaxies with a range of star formation surface densities and sizes will be observed. Observations of distant galaxies generally have limited spatial information and no vertical information, requiring analysis of the entire galaxy as a single point or assuming it is a uniform cloud or thin disk. [C II] and [O III] are the brightest rest-frame far-infrared lines and the first to be seen at high redshift e.g. with ALMA. Halos of galaxies are being actively studied at X-ray (Chandra) and radio (JVLA) wavelengths. We will measure the vertical distribution traced by the main cooling line of the cold interstellar medium, [C II], and the best far-infrared line tracer of ionized halo gas, [O III].
Proposal ID: 06_0011
Principal Investigator: James De Buizer (Universities Space Research Association)
Title: Revealing the Embedded Structures and Sources within Giant HII Regions: Wrapping up the Survey
Abstract: Most studies concentrate on the processes of isolated low-mass star formation while little is known about massive star formation and clustered star formation, despite the fact that the vast majority of stars are formed within OB clusters. Giant HII regions harbor the most active areas of OB star formation in the Galaxy, and as such are fantastic laboratories for the study of massive star formation as well as clustered star formation. However, most of these GHII regions are optically obscured and far away, requiring them to be studied in the MIR/FIR with adequate spatial resolution. SOFIA 19.7 and 37.1µm imaging with approximately 3 arcsecond resolution well-suited for revealing the embedded structures and sources within these regions. These SOFIA observations will be combined with data taken at other wavelengths to quantify the detailed physical properties within GHII regions individually and as a population. The observations will also expose the areas of the youngest stages of massive star formation within the GHII regions and allow for the confirmation or confrontation of the recently proposed evolutionary sequence of GHII regions. GHII regions are a dominant source of emission contributing to the bolometric luminosity that we see from galaxies in general. Therefore, understanding the global and detailed properties of GHII regions in our own Galaxy can be used as a template for interpreting what we observe in galaxies far away.
Proposal ID: 06_0012
Principal Investigator: Dan Clemens (Boston University)
Title: The Magnetic Fields of the Dense and Diffuse Cores in L1544
Abstract: We propose higher angular resolution (HAWC+ D-band) and deeper polarimetric observations (twice the integration time) than the tabulated ROC plan for the dense core of the nearby (140 pc) dark cloud L1544. We will use these data to test ambipolar diffusion models of this pre-stellar core and to critically compare HAWC+ polarimetric maps to our near-infrared background starlight polarimetry and reprocessed SCUPOL map of the B-field of this cloud. Further, we propose sensitive HAWC+ E-band polarimetric observations of the outer, more diffuse pair of cloud cores (L1544 E and L1544 W) located outside the ROC FOV. These HAWC+ data will permit comparing how the B-field strengths (from the Chandrasekhar-Fermi method) vary with radial offset for the diffuse and dense cores. All of these data, taken together, will permit quantitative comparisons of position angle structure functions to assess the ratio of random to uniform B-field strengths in each core.
Proposal ID: 06_0013
Principal Investigator: Dan Clemens (Boston University)
Title: Magnetic Fields in The Low-Mass Star-Forming Dark Cloud B5 and B5IRS1
Abstract: SOFIA/HAWC+ is uniquely suited to reveal the magnetic field conditions in the infrared opaque core of the low-mass star-forming dark cloud B5 and its YSO, B5IRS1. Previous optical polarimetry provided 1/2 degree-scale context, and our recent Mimir H-band NIR polarimetry reveals the plane-of-sky B-field over some of the B5 cloud, but along only a few lines of sight. Herschel has shown that the central dark core and its two fainter filaments are bright enough for HAWC+E polarimetry and should return over 600 pixel detections. This permits making detailed B-field strength comparisons between existing Zeeman studies and those estimated from SOFIA/HAWC+ polarization position angle dispersions. Such comparisons are critical to assessing the applicability of this Chandrasekhar-Fermi dispersion method for estimating magnetic field strengths. Additionally, IRS1 was detected in H and K band polarization, showing Serkowski-like polarization wavelength dependence, which is at odds with models of scattering disks around YSOs. HAWC+A polarization observations of this YSO would reveal both the disk physical orientation and its embedded magnetic field properties.
Proposal ID: 06_0014
Principal Investigator: Dan Clemens (Boston University)
Title: Multi-Scale Probes of Magnetic Fields in HII Region Cores and Clouds with Zeeman Detections
Abstract: Polarimetric observations using HAWC+ in its E (214 µm) and A (53 µm) modes are proposed toward three massive-star forming Giant Molecular Cloud cores: S106, S140, and DR21OH. These observations will reveal and characterize the magnetic fields of these cores over sizes from 1000 AU to several parsecs, connecting to magnetic fields probed by background starlight near-infrared polarimetry in the cloud peripheries. The short wavelength HAWC+ mode will accurately measure the dispersion in polarization position angles within the same beamsize locations where Zeeman effect field strengths have already been measured using OH and CN. This will enable testing and calibrating the Chandrasekhar-Fermi (1953) method of estimating magnetic field strengths against the Zeeman detections for each of these cloud cores. Such a comparison is a necessary first step in assessing magnetic field strengths across the cloud cores to evaluate the relative importance of the magnetic field to gas dynamics and gravity in the cloud and star formation processes.
Proposal ID: 06_0015
Principal Investigator: David Neufeld (The Johns Hopkins University)
Title: Terahertz water masers
Abstract: Using the GREAT instrument, we will observe terahertz water masers toward seven oxygen-rich evolved stars with circumstellar envelopes that emit maser radiation in the 22 and 321 GHz water transitions: o Cet, U Ori, R Leo, R Crt, RS Vir, S CrB and R Cas. We will also observe three water maser positions in star-forming interstellar gas -- W49N, W51 (Main) and W51 (IRS2) -- all of which are strong sources of 22 GHz and submillimeter water maser emissions. Our primary target will be the 8(27)-7(34) line of water vapor at 1296.411 GHz, a transition that our models predicted would be a strong maser - a prediction recently confirmed by our Cycle 4 observations of three evolved stars: W Hya, U Her and VY CMa. This transition, which was not accessible with Herschel/HIFI, has a significantly higher frequency than any water maser transition observed to date. In combination with ground-based maser observations at lower frequencies, the proposed observations will provide new constraints on the conditions of gas temperature, gas density, and IR radiation field within the maser-emitting region, providing important information about the maser pumping mechanism.
Proposal ID: 06_0017
Principal Investigator: David Neufeld (Johns Hopkins University)
Title: Probing the molecular hydrogen fraction in diffuse molecular clouds with observations of HCl+
Abstract: Using the GREAT instrument, we will observe the Doublet Pi 3/2 J = 5/2 - 3/2 transitions of the H-37Cl+ and (where not already observed in Cycle 4) the H-35Cl+ molecular ions at 1.442 and 1.444 THz, in absorption, toward the bright continuum sources Sgr B2 (M), W31C (G10.6-0.4), and W49N. The observations will yield robust estimates of the HCl+ column densities in diffuse clouds lying along the sight-lines to those sources. Because HCl+ reacts rapidly and exothermically with H2 to yield H2Cl+, the abundance ratio HCl+/H2Cl+ is sensitive to the H2 abundance in the interstellar gas; combining the HCl+ measurements with ones already available for H2Cl+ will thus permit independent estimates of the molecular hydrogen fraction along the proposed sight-lines. This proposal follows up on a successful detection of HCl+ obtained in a pilot program performed in Cycle 4.
Proposal ID: 06_0019
Principal Investigator: Dominik Riechers (Cornell University)
Title: Dissecting an AGN-Starburst System at Redshift 4 with SOFIA
Abstract: Studies of AGN-starburst systems at high redshift over the past decade have revealed massive dust reservoirs in many of them, suggesting dust-obscured star formation rates in excess of 1000 Msun/yr if heated by massive star formation. However, due to a lack of constraints at observed-frame far-infrared wavelengths, the contribution of AGN to the dust heating is still an active subject of debate. We here propose a demonstration of the utility of SOFIA/HAWC+ to significantly improve our understanding of this issue in the early universe by decomposing the dust SED of a luminous AGN- starburst system at redshift 4. Our target, the unique lensed galaxy APM 08279+5255, is the apparently most luminous galaxy in the universe, with an apparent bolometric luminosity of 7 x 10^15 Lsun, ~20% of which is radiated away at (far-) infrared wavelengths. The proposed inexpensive photometry at 53, 89, 153 and 214 micron (only ~30min on source total) will yield dramatically improved constraints on the warm dust peak powered by the AGN compared to the original, moderate signal-to-noise ratio IRAS detection, enabling a detailed decomposition of the dust spectrum to measure the dust masses, temperatures and opacities of different components. This will establish SOFIA as a key probe of early cosmic epochs, back to ~1.5 billion years after the Big Bang.
Proposal ID: 06_0020
Principal Investigator: Paul Goldsmith (JPL)
Title: Calibrating [NII] Emission from HII Regions
Abstract: Fine structure lines are important tools for understanding star formation and energetics in the Milky Way and external galaxies. The [NII] fine structure transitions are excellent probes of massive young stars, due N+ being found only in the fully ionized gas that these stars produce. We propose to compare SOFIA/upGREAT observations of the 205 micron [NII] line in 14 Galactic HII regions with radio continuum and radio recombination line (RRL) observations of these sources. With these data, we will be able to study the correlation of [NII] intensity with the emission measure and the electron column density and to see how well RRL, radio continuum emission, and [NII] emission compare as tracers of massive star formation and of the energy input from massive young stars to their associated ionized material. We will use the high resolution of upGREAT to spectrally resolve the [NII] emission, which will be critical for calculating the [CII] intensity from the [HII] region and comparing with measurements to obtain information on possible saturation of [CII] emission. Comparing [NII} and RRL spectra allows us to investigate the electron density distribution, and offers the possibility to observe absorption by N+ in the diffuse medium along the line of sight. For four strong sources that are moderately extended on the 20” angular scale of the SOFA beam at 205 microns, we will make cuts using OTF observations of the [NII] emission to compare in detail the variation of emission and electron density, and to extend the correlation of the [NII] intensity and electron column density and emission measure. Simultaneous observation of the [OI] 63 micron line will allow modeling of the PDRs associated with the HII regions, and develop a similar calibration for the emission and energetics of neutral gas associated with massive star formation.
Proposal ID: 06_0021
Principal Investigator: David Chuss (Villanova University)
Title: A Polarimetric Survey of the Cool Dust in the Central Molecular Zone of the Milky Way
Abstract: We propose a 214 µm polarimetric survey of the Central Molecular Zone (CMZ) of the Galaxy using the HAWC+ polarimeter. This survey will provide an unprecedented combi- nation of coverage, sensitivity, and angular resolution of the magnetic field geometry in the cool dust component of the Galactic center. The new data, which will consist of a map of thousands of independent polarization measurements across the CMZ, will help to deter- mine the geometry and strength of the magnetic field in this complex region. It is known that the Galactic center contains strong magnetic fields, but their role in the dynamics of the region is not well understood. The geometry and field strength is likely to vary with the three-dimensional location within the CMZ. Herschel observations have clearly separated two populations of dust within the CMZ: a warmer component (30-40K) and a cooler component (10-15 K). HAWC+/SOFIA is uniquely positioned to provide the most complete picture of the field in the CMZ dust to date and will help answer this important questions of Galactic center field strength and geometry. This proposal will provide the field configuration in the cool dust component. It will test the kinematics of this component and provide critical complementary information to the warm dust survey that will be done as part of the ROC observations.
Proposal ID: 06_0022
Principal Investigator: David Neufeld (Johns Hopkins University)
Title: Kinematics of shock-heated H2 with EXES
Abstract: Shock waves are a ubiquitous phenomenon in the interstellar gas, and may cause the heating, compression, dissociation, and/or ionization of the gas through which they propagate. By carrying out velocity-resolved observations of the mid-IR H2 emission lines that dominate the emission from shocks propagating in molecular gas, and interpreting them in the context of state-of-the-art shock models, we will place unique constraints on the physics of molecular shocks. The key measurement technique utilized in this investigation is spectroscopy of the S(4) -- S(7) pure rotational lines of H2. We will use EXES in the high-low mode to obtain high-resolution spectra of these transitions in emission toward positions C1 and E in HH54, or toward two positions in the bow shock in HH7. The resultant spectra will provide a definitive probe of the kinematics of the warm, shocked-heated H2 in the source; carefully interpreted, they will provide unique information about the structure of interstellar shock waves and the conversion of para-H2 to ortho-H2 within molecular shocks.
Proposal ID: 06_0026
Principal Investigator: William Langer (Jet Propulsion Laboratory, Caltech)
Title: Distribution and Properties of Highly Ionized Galactic Gas Revealed By [NII] and [CII]
Abstract: The distribution of atomic and molecular hydrogen in the interstellar medium has been conducted with 21-cm HI, and mm and submm CO, and other trace molecules. However, the regions where UV and FUV are unshielded are much less explored including diffuse molecular (CO-dark H2) clouds, photon dominated regions (PDRs), and fully ionized gas where FUV radiation photoionizes hydrogen and metals. This highly ionized gas exists in various states over a wide range of densities from the hot coronal gas, warm ionized medium (WIM), to the dense HII regions and cloud ionized boundary layers. The fine structure lines of C+, [CII] at 158 µm, and N+, [NII] at 205 and 122 µm are important probes of the ionized gas. Herschel enabled a sparse [CII] survey of the Galactic disk with HIFI and [NII] with PACS. The velocity resolved [CII] survey (GOT C+) produced a radial profile of the Galaxy in [CII] and statistical sampling of thousands of interstellar clouds. The PACS survey of 140 GOT C+ lines of sight could not produce a comparable data base because the unresolved spectra could not disentangle line-of-sight structure. We propose a limited survey in [NII] and simultaneously [OI] of 15 lines of sight at b = 0o between longitudes 10o and 30o, previously surveyed in [CII] with HIFI and [NII] with PACS, to distinguish among different sources of highly ionized gas. We will also observe 30 necessary reference positions at b > 0o. Our interpretation of all 45 LOS will be aided by a radio recombination line survey of ionized regions towards these targets under a separate program. A spectrally resolved picture of a portion of the Galactic plane will determine the radial and vertical, z, distribution of electrons, resolve the relative [C II] emission among the weakly and highly ionized ISM components, reveal the interaction of spiral arm potential with the inter-arm WIM, and recalibrate the [C II] star formation relationship.
Proposal ID: 06_0027
Principal Investigator: Ian Stephens (Smithsonian Institution Astrophysical Observatory)
Title: The Role of Magnetic Fields in High-Mass Star-Forming Filaments
Abstract: Filaments are ubiquitous in the star formation process. Planck has revealed that magnetic fields are perpendicular to the densest filaments, which are the birthplace of high-mass stars, suggesting that fields help funnel gas into the filaments. However, the resolved field morphologies and strengths in the dense filaments are unknown. We propose HAWC+ 53 and 214 µm polarimetric observations toward two high-mass filaments, the Snake (G11.1) and G18.6, to unveil the field morphology. Such observations will probe the filament field morphology at the subarcminute scale over the largest spatial extent to date: 25 and 9 pc respectively. We expect to detect polarization for over 400 independent beams. From the field morphology, we will test the hub-filament theory and investigate how the magnetic field strength and morphology changes with evolution and size-scale.
Proposal ID: 06_0028
Principal Investigator: Jorge Pineda (Jet Propulsion Laboratory)
Title: Tracing the evolution of the interstellar medium and star formation across the spiral arms of M51 with [NII]
Abstract: The evolution of the interstellar medium (ISM) and star formation across spiral arms is a fundamental process that regulates star formation in galaxies and therefore drives their evolution. The different stages of ISM evolution can be traced with HI, CO, Halpha [CII], and FUV observations. However, we lack observations of unobscured tracers of ionized gas that be used to isolate regions in the early stages of massive star formation at high spectral resolution. We propose to observe a 10 position cut across a spiral arm in [NII] 205µm in the M51 galaxy with the 4GREAT instrument on SOFIA. Recent results from the [CII] map of M51 observed with SOFIA upGREAT and FIFI-LS have revealed a specific spatial-velocity structure between CO, [CII], and FUV emission suggesting a spatial-velocity separation of different stages of ISM evolution.While the [CII] line can trace ionized, atomic, and diffuse and dense molecular gas in PDRs, the [NII] emission only arises from fully ionized regions that are associated with massive young stars, as the ionization potential of nitrogen is higher than those for hydrogen and carbon. The proposed [NII] observations are needed to isolate the location of newly formed stars in position/velocity space, thus further constraining the distribution of the different stages of the ISM evolution in M51. The proposed observations will be combined with a multi-wavelength set of observations coming from several observatories including Herschel, Spitzer, and GALEX, and will certainly motivate follow up observations with current and future observatories such as NOEMA and JWST. Additionally, the proposed work will provide important constraints to theoretical models of star formation resulting from the passing of a spiral density waves in galaxy disks. We will use the [NII] 205µm emission to determine the spatial and spectral structure of highly ionized gas across a spiral arm in M51, thereby pinpointing the precise location of active star formation. We will combine the [NII] observations with different ISM tracers to determine the timescales at which the ISM evolves and star formation takes place along the spiral arms of M51. We will also study the line width of the [NII] and [CII] emission to study the effects of stellar feedback on the ISM. Finally, we will use [NII] to determine the contribution from ionized gas to the [CII] emission.
Proposal ID: 06_0029
Principal Investigator: Yoshiki Toba (Academia Sinica Institute of Astronomy and Astrophysics (ASIAA)
Title: Dust properties of one of the most luminous IR galaxies in the Universe
Abstract: We propose follow-up observations with HAWC+ of an extremely infrared (IR) luminous galaxy at z=3.70, selected with its extremely red optical/IR color. Our Spectral Energy Distribution (SED) fitting of its WISE, SCUBA-2, and SMA photometry indicates an IR luminosity in excess of 10^14 Lsun, making it one of the most luminous IR galaxies in the Universe, only next to W2245-5026 (2.2x10^14 Lsun). However, the lack of 80-200 µm photometry produces substantial uncertainties in its IR luminosity and the nature of the IR emission. This can be resolved with the proposed HAWC+ observations. In addition, our target is rich in dust and its optical spectrum suggests a type 1 AGN with broad emission lines. In order to interpret the above, we will investigate dust properties based on a detailed SED modeling where HAWC+ data are critical to constrain its rest-frame mid-IR SED. The proposed observations will enable us not only to determine precise IR luminosity of our target but also to reveal the dust mass, temperature, and dust obscuration for the extremely luminous dust-obscured AGN, and shed light on the co-evolution of AGN and galaxies in the distant universe.
Proposal ID: 06_0031
Principal Investigator: Terry Jones (University of Minnesota)
Title: Grain Alignment in Mass-Loss Winds
Abstract: Magnetic fields are present in stars and stellar winds at all phases of stellar evolution. For massive stars, they may have a strong effect on the mass-loss mechanism and mass-loss history of these stars. One of the major techniques for measuring the magnetic field geometry is polarized thermal emission from dust grains aligned by a local magnetic field. This has been well demonstrated in the interstellar medium, but only hinted at in the much smaller confines of dusty, mass-loss winds. We propose to test for polarized thermal emission from aligned dust grains in the dusty, asymmetric winds of warm and cool luminous stars at Far Infrared Wavelengths using HAWC+. This work will lead to the study of polarized thermal emission and magnetic field geometries in these winds at high spatial resolution from the ground at 10 microns and millimeter waves.
Proposal ID: 06_0032
Principal Investigator: Dario Fadda (SOFIA Science Center (USRA)
Title: An infrared tsunami in NGC 2445
Abstract: We propose to observe with HAWC+ and FIFI-LS the ring of NGC 2445, an "off-center" collisional ring galaxy with bright knots of star formation and strong emission of warm H2. These observations will sample the peak of the far-IR continuum in the ring complementing existing Spitzer and Galex observations and allowing us to estimate the total emission from the far-UV to the far-IR, hence the total star formation. With FIFI-LS we will explore the effect of the shock on the main cooling lines: [OIII]63µm and [CII]157.8µm. We expect these lines to be substantially boosted by the shock, well beyond the values expected for the star formation inferred in the knots. If this is correct, the [CII] emission may not peak on the HII regions but may have a more ring-like distribution. The relative strength of cooling lines versus star formation rate will provide a better estimate of the effects of the shock along the ring and a way of estimating how turbulence can affect star formation estimates based on [CII] emission.
Proposal ID: 06_0038
Principal Investigator: B-G Andersson (SOFIA Science Center, USRA)
Title: Radiative Alignment and Grain Mineralogy - SOFIA observations of IK Tau and IRC+10216
Abstract: Dust induced polarization is a potentially very powerful tool for studying magnetic fields in varied environments, from the diffuse and dense interstellar medium, circumstellar disks and envelopes, and the Solar System. However, to reliably interpret the polarization data a full understanding of grain alignment physics is needed. Over the last couple of decades a quantitative theory has been developed and partially tested. Observational tests of this Radiative Alignment Torque (RAT) theory have -- so far -- generally supported the theoretical predictions. The influence of grain mineralogy on the alignment is, however, one area that has not yet been directly probed. In RAT theory, the alignment with the magnetic field requires the grains to be paramagnetic; fulfilled by the silicates. However, the second major component of interstellar dust - the carbon grains - is expected to be diamagnetic and should not align. We have started to probe this prediction by acquiring SOFIA/HAWC+ (Cy4/5) observations of the carbon-rich circumstellar envelope of IRC+10216. Under the RAT paradigm, these (recently acquired) observations show both expected and surprising results. The polarization in IRC+10216 is highly centro-symmetric (as expected), but oriented in the radial, rather than azimuthal, direction (unexpected). These results can be understood if the carbon grains are aligned by the RAT mechanism, but do not achieve internal alignment. To test this interpretation we need to 1) verify the theoretical conclusion that RAT alignment is strongly dominant over mechanical alignment and 2) observationally probe the importance of internal alignment for para- and dia-magnetic grains. Here, we propose to address these questions by observing also the brightest oxygen-rich AGB star, IK Tau, with HAWC+ polarimetry. In addition, to accurately probe the dust temperature variations in the shells we request FORCAST MIR imaging of the two circumstellar envelopes.
Proposal ID: 06_0039
Principal Investigator: Dan Clemens (Boston University)
Title: Magnetic Fields in Two Infrared Dark Clouds
Abstract: The role of the Galactic magnetic field in cloud and star formation, despite decades of study, is still debated. In this project, we will test the importance of magnetic fields in the formation and evolution of Infrared Dark Clouds (IRDCs). IRDCs are expected to host the formation of stellar clusters and high-mass stars, and with them, most of the stars in the Galaxy. Due to the high densities of IRDCs, optical and near-IR (NIR) polarimetry cannot probe the magnetic field in the dense cloud interiors where star formation occurs. Therefore, dust emission polarimetry is necessary to reveal the magnetic field in these clouds. We request polarimetric observations of two IRDCs in the first Galactic quadrant using the SOFIA HAWC+ instrument in E band. HAWC+ is the only instrument that can efficiently map the dust polarizations of whole clouds. Using HAWC+ dust emission polarimetry of the interiors of the IRDCs, in conjunction with NIR polarimetry of the IRDC surroundings, we will determine whether the magnetic field changes direction or strength as a function of cloud density.
Proposal ID: 06_0040
Principal Investigator: Justin Spilker (University of Texas at Austin)
Title: Using High-Ionization Lines in Low-Metallicity Galaxies to Calibrate a Purely FIR Metallicity Diagnostics
Abstract: The gas-phase metallicity of the interstellar medium (ISM) is a fundamental property of galaxies: it is closely correlated with galaxy mass, provides a record of the gas cycling in and out of galaxies, and regulates the heating and cooling of the ISM. Traditional optical strong-line diagnostics of metallicity are subject to factor-of-5 systematic uncertainties, mainly due to the effects of uncertain electron temperature and dust obscuration. These have led to disagreement over the evolution of the mass-metallicity relation at high redshifts and whether systematics are due to real differences in abundance ratios or simply the effects of dust or radiation field intensity. Here, we propose to calibrate and validate a metallicity diagnostic based solely on FIR fine structure lines, which are unaffected by extinction and less susceptible to temperature effects. Our observations target the OIII 52µm and NIII 57µm lines in a sample of three nearby low-metallicity dwarf galaxies, exploiting the unique short-wavelength coverage of FIFI-LS on board SOFIA. Along with archival SOFIA/FIFI-LS, Herschel/PACS, and ISO/LWS observations, we will calibrate this diagnostic over an order of magnitude in metallicity. This diagnostic will reduce the systematic uncertainties present in optical methods by a factor of 3, and will be especially useful for highly dust-obscured systems, which become increasingly abundant in the early universe. Finally, our observations lay the foundation for future metallicity determinations at higher redshifts, as the necessary lines will be accessible to SPICA up to z=1.5, a future Far-IR Surveyor mission to z~6, and ALMA at z>5.
Proposal ID: 06_0041
Principal Investigator: Michael Kaufman (San Jose State University)
Title: A GREAT Map in M20: [OI] and [CII] Emission from a Young Star Forming Region
Abstract: Using GREAT to mapping a region of strong [OI] 63µm and [CII] 158µm line emission in the Trifid Nebula (M20), and comparing our results with existing infrared continuum maps from Herschel and Spitzer, we will be able to study the physical conditions in this very young massive star forming region which contains a well-defined, bright, edge-on PDR, a photoevaporating globule with an embedded protostar, several cometary globules, and protostellar jets. Using the velocity-resolved spectra, we will be able to measure the relative contributions of PDRs, outflows and other kinematic components to the FIR emission. Mapping an additional high-J CO line allows us to further distinguish high-excitation outflows from PDRs. Since the FUV radiation illuminating the PDRs is dominated by a single O7.5 star in the emission nebula, and is hence well characterized, we can then compare our models with the PDR contributions to the FIR lines.
Proposal ID: 06_0042
Principal Investigator: Jonathan Tan (University of Florida)
Title: The SOFIA Massive (SOMA) Star Formation Survey - High Priority Protostars
Abstract: The SOMA Survey is a multi-cycle project to build a large, high legacy value sample of high- and intermediate-mass protostars that are uniformly observed across MIR and FIR bands to test theoretical models of massive star formation. Here we propose to observe about 20 high priority massive protostars with SOFIA-FORCAST with this Regular Program proposal, which will result in near completion of the survey. Source selection is driven by the desire to have good sampling of all evolutionary and environmental types. Especially the unique 37 micron imaging reveals thermal emission from outflow cavities and the relative fluxes from the near and far-facing sides probes the amount of dense gas in the immediate vicinity of the protostar. Core Accretion models generally involve larger quantities of such gas than Competitive Accretion models. We will compare observational results against specific predictions of a suite of radiative transfer simulations to make quantitative tests of the models. We also propose this project as a Thesis Enabling Program, leading to the education and training of Ph.D. student Ms. Mengyao Liu.
Proposal ID: 06_0043
Principal Investigator: Jeonghee Rho (SETI Institute )
Title: Velocity-Resolved [OI] Line Survey of Supernova Remnants Interacting with Molecular Clouds
Abstract: Supernova remnants interacting with dense molecular clouds (MSNRs) provide astrochemical laboratories to study heating and cooling of the dense ISM, shock dynamics, and reformation of molecules. Models and observations show that the cooling budget in shocks and the dense ISM is dominated by [O I], CO, water and OH lines at far-IR wavelengths. However, our understanding of these cooling lines and shock properties is still very limited because of the very poor angular resolution and velocity information provided by observing facilities such as ISO, Spitzer, and Herschel. This renders the interpretation of such observations difficult especially for distant objects in our Galaxy and external galaxies (e.g. with ALMA). We propose to study the evolution of the primary contributors of the far-IR line cooling through observations of MSNRs. We selected a set of MSNRs which showed 63 micron [O I] using Spitzer MIPS SED. We propose 63 micron [O I] and CO(16-15) observations with SOFIA/upGREAT towards these 10 Spitzer-detected MSNRs. Our goals are i) to resolve velocity components of the key shock diagnostic lines of [O I] and CO, ii) to determine if these lines are produced by slow or fast shocks and derive their shock parameters, iii) to study their cooling budget and chemical abundances by combining ground-based low-J CO and Spitzer mid-IR observations, and iv) to understand shock properties and their association with accelerated high energy particles. Proposed high-resolution velocity information of this uniform sample of MSNRs will be critical to understand future JWST observations in mid-IR.
Proposal ID: 06_0044
Principal Investigator: Lizette Guzman-Ramirez (Leiden Observatory)
Title: Understanding the Nebular Abundance Discrepancy Problem with SOFIA
Abstract: The abundance discrepancy between recombination and collisional lines is a long-standing open question for planetary nebulae and HII regions. For planetary nebulae (PNe), C, N, O, and Ne abundances as derived from optical recombination lines (ORLs) are typically a factor of ~5 or more higher than the values inferred from collisional lines. This ratio is called the abundance discrepancy factor (adf). A promising proposition to explain this long-standing nebular abundance problem posits that these nebulae contain (at least) two distinct media - one of "normal" electron temperature, Te (~10000 K) and chemical composition (~solar) and another of very low Te (<~1000) that is H-deficient, thus having high metal abundances relative to H. The latter component emits strong heavy element ORLs and IR fine-structure (FS) collisionally excited lines (CELs), but essentially no optical/UV CELs. These clumps have eluded direct detection thus far, but this year Garcia-Rojas et al. (2016) found evidence of these clumps in the PN NGC 6778. On the other hand, there is mounting circumstantial evidence for their existence, Yuan et al. (2011) modelled the high-adf PN NGC 6153 using a 3-D photoionization code. The models that included the low Te, H-deficient clumps fit most observations far better than did those models without the clumps. It has been shown that the adf varies with position in a PN and is highest close to the central star. The very low Te clumps must be cooled predominantly by FS mid-IR lines. We propose to use FORCAST grisms to map mid-IR FS lines in a sample of PNe to compare the co-spatial optical and IR CELs where the adf peaks.
Principal Investigator: Jochen Eisloeffel (Thueringer Landessternwarte)
Title: Probing jets from young embedded sources
Abstract: The bipolar flows from newly born protostars play an important role in transporting the angular momentum accumulated in the accretion disk away from the forming star, and therefore offer a unique opportunity to investigate the accretion properties of the protostar and the related energy budget. This field will soon be revolutionised thanks to JWST, which will be able to penetrate dusty protostellar envelopes with unprecedented sensitivity and resolution in the IR, thus exploring the Class 0/I disk-star interaction region with the same level of detail that is now possible on T Tauri stars. The JWST, however, which is efficient in the IR spectral range up to 30microns, does not cover all the relevant excitation regimes present in the jet cooling regions. Consequently, it is essential to gather complementary information from lines in different spectral ranges for a correct interpretation of the JWST results. We propose to obtain FIFI-LS spectroscopic maps of three prototypical collimated bipolar outflows driven by Class O/I protostars that we are planning to propose for JWST Cycle 1 in the 63micon and 145micron transitions of [OI]. These maps will enable us to to study the extent of warm low excitation atomic gas in these flows, to derive the mass flux rate in the atomic jet, and measure the accretion/ejection ratio of matter in Class 0/I sources. The combination of SOFIA FIFI-LS and JWST MIRI observations of Class 0/I jets will provide an unprecedented detailed view of Class 0/I jets all owing one a direct comparison with more evolved T Tauri stars.
Proposal ID: 06_0047
Principal Investigator: Dan Clemens ( Boston University)
Title: Nature or Nurture: Multi-Scale Magnetic Fields in the L1448 Star Forming Dark Cloud
Abstract: The low-mass star-forming dark molecular cloud L1448 has recently had its envelope magnetic field characterized through extensive near-infrared (NIR) background starlight polarimetry, using the Mimir instrument. These data reveal an envelope magnetic field that smoothly varies in a nearly identical fashion to the cloud structure, as both undergo a 90 deg bend on the sky. Further, the jets, outflows, and bullet ejections from the embedded YSOs appear to also share the same coherent bending. Are these effects coincidental or coordinated? Is the revealed magnetic field strong (driving the 'nature') or is it weak and merely responding to external forces (hence affected more by 'nurture')? The NIR polarization alone cannot probe into the high extinctions necessary to answer these questions. Only HAWC+ with its powerful far-infrared polarimetry modes can obtain the 300-1000 independent samples needed to tease out the density and location dependences of the magnetic field orientation angles (and their dispersions) that will permit separating and identifying the relative roles for nature and nurture in simple dark cloud setting such as found in L1448.
Proposal ID: 06_0049
Principal Investigator: Raghvendra Sahai (Jet Propulsion Laboratory)
Title: Probing the Mass-Ejection Process Leading to the Formation of Young Planetary Nebulae
Abstract: Planetary Nebulae represent the bright end-stages of most stars in the Universe, yet their formation is poorly understood. Although one expects the round circumstellar shells that are found around most AGB stars to evolve into round PNe, such PNe are exceedingly rare, and aspherical PNe (e.g., bipolar, multipolar and elliptical) are quite common. There is now mounting evidence that a phase of extreme mass-loss at end of the asymptotic red giant (AGB) phase (the "superwind") leads to the formation of most aspherical PNe and likely results from strong binary interactions (e.g., common-envelope) which can, directly or indirectly, produce dense dusty waists and high-speed jets and may therefore be the primary cause behind the dazzling variety of PNe shapes that are observed. But the superwind phase is very poorly understood, and a major impediment to progress is that there is no systematic survey of the mass ejecta due to the superwind in young PNe. Existing observations of ionized and molecular gas probe only minor components of the total mass budget. We propose a SOFIA study to directly probe the bulk of the mass ejecta, which lies in the photon-dominated region (PDR) that surrounds the ionized central region, for a small sample of young PNe (selected from the HST survey by Sahai et al. 2011). We will use GREAT to observe the fine-structure lines of CII(158mu) and OI(63mu) from our sample, as these are the best probes of the neutral gas in the PDR. We will determine the mass, mass-loss rates and outflow speeds characterizing the ejecta, and their dependence on morphology, which will provide tests of binary interaction models for PN formation. We will use the CLOUDY code to model our objects and improve upon the above estimates of the mass in atomic gas and the mass-loss rate.
Proposal ID: 06_0051
Principal Investigator: Bo Reipurt (Institute for Astronomy, University of Hawaii)
Title: Multiple Protostars and Small Protostellar Clusters: The Impact of Dynamical Evolution
Abstract: Small compact groups of newborn stars form non-hierarchical configurations that are dynamically unstable. The resulting chaotic motions lead to repeated expulsions of individual components of the group, often the least massive members, to the outskirts of the infalling core thus controlling the growth of the protostars. Some of these ejections lead to escapes, others to tenuously bound orbits. The ejected members suffer truncation of the outer, cooler layers of their circumstellar material, leading to changes in their energy distributions. This has been studied theoretically, but not yet observationally. We propose to image four small, compact complexes of protostars at mid-infrared wavelengths, specifically at 19, 24, 31, and 37 micron using FORCAST in order to examine the flux distribution of the individual members, for a comparison with results from numerical models. SOFIA is the ideal facility for such mid-infrared observations because of its high sensitivity and because it is significantly better than WISE and Spitzer to resolve the individual members of such compact newborn clusters of protostars, a pre-requisite for accurate photometry.
Proposal ID: 06_0052
Principal Investigator: Patrick Morris (IPAC/Caltech )
Title: Evolution of the Molecules and Dust in the Eruptive Environment of the Massive Binary System eta Carinae
Abstract: Light molecules bearing N, C, and O recently detected in the massive, unstable binary star eta Carinae with Herschel and from the ground provide key information on thermal and chemical conditions inside the massive "Homunculus" eruption nebula which can support molecule and dust condensation and survival. The dust chemistry and molecular abundances reflect CNO-cycled material from the erupting star, which has been proposed to be the product of a stellar merger. These circumstances provide important context for similar energetic events observed in other galaxies (e.g., supernova imposters and Type II supernovae), and on dust in the early Universe. The molecules have been observed mainly near apastron of the highly eccentric 5.54-yr orbit. The system is entering phase 0.75 in Summer 2018, which is an ideal time to gauge the spectroscopic evolution of the molecules and dust in relation to the energetic colliding stellar winds, and in preparation for the periastron event in 02/2020. We propose to carry out an analysis of the excitation and emitting volume properties of the molecular gas from observations of 12,13CO, 12,13CH+, and N2H+ transitions, using GREAT and FIFI-LS. The data will allow us to ascertain whether the cool dust continuum reflects further evidence for decreases in the IR luminosity of the system as well. We are requesting a total of 4.6 hours (USPOT time) for the Cycle 6 2018 southern deployment.
Proposal ID: 06_0054
Principal Investigator: Sarah Ragan (Cardiff University)
Title: Tracing molecular cloud formation
Abstract: Molecular cloud formation is a long-standing puzzle in studies of the interstellar medium. A leading theory for cloud formation is the collision of large-scale gas flows, simulations of which show that this process can effectively assemble clouds matching observed properties. Due to fast formation of molecular hydrogen from HI but slow production of detectable CO, direct observational confirmation of this picture has been difficult to obtain. [CII] emission is expected to be associated with inflowing gas. Based on our initial study of cloud tracers in the molecular, atomic and ionised phases of carbon, we identified an excellent candidate cloud, G48, with which to test the converging flow scenario. G48 exhibits extended [CII] emission with a large velocity gradient perpendicular to the dense, quiescent filament which cannot be explained by ionisation by embedded protostars. We propose to map [CII] with upGREAT in two regions bordering our existing map in order to test whether the [CII] originates predominantly from diffuse inflowing gas or from within the extended molecular cloud. These observations could for the first time provide observational constraints on the properties of converging gas flows responsible for molecular cloud formation.
Proposal ID: 06_0056
Principal Investigator: Kathleen Kraemer (Boston College)
Title: Water Absorption in Late-Type M Giants
Abstract: We propose to use the high spectral resolution, high sensitivity of EXES on SOFIA to characterize the water absorption features at 6.6-6.7 micron in a set of M4-M6 giants. We have detected surprisingly strong absorption features from water vapor in late-type M giants in low spectral resolution data from ISO's SWS and Spitzer's IRS. Those data were too coarse, though, to fully characterize the physical conditions under which the features form. The EXES observations will enable us to fit models to the numerous high temperature absorption lines present in this spectral region, determining the gas temperature and pressure and thus where the absorbing gas layer resides. We will obtain EXES spectra at R=50,000 centered at 6.6887 micron for each of our targets. The water transition at this wavelength is not a strong feature in the low temperatures of the Earth's atmosphere but often is at the higher temperatures of M star atmospheres. Numerous other relatively high temperature transitions will also be within the EXES bandpass at the settings we will use. We will compare the line ratios from these transitions with our models to determine the temperature and height above the photosphere of the gas. These data will also allow us to determine the best transitions for spectra from the MIRI instrument on JWST, which has better spectral resolution than SWS and IRS but lower than EXES, to use to characterize the water features in similar stars. We request 6.7 hours of EXES time to complete this study.
Proposal ID: 06_0058
Principal Investigator: Jonathan Tan (University of Florida)
Title: The SOFIA Massive (SOMA) Star Formation Survey Program
Abstract: The SOMA Survey is a multi-cycle project to build a large, high legacy value sample of high- and intermediate-mass protostars that are uniformly observed across MIR and FIR bands to test theoretical models of massive star formation. It is currently about 50% complete. Together with a companion Regular Program proposal targeting high priority sources in the Galactic plane, here we propose a Survey Program, which enables the completion of the survey. From our experience of previously being selected as a Survey Program, we expect that this proposal may yield up to ~10, mostly intermediate-mass sources, which will complement the higher-mass sources we observe via the Regular Program. Overall, this will lead to a survey sample that probes a range of protostellar masses, evolutionary states and environments, with enough protostars in each source type to allow averaging over random effects associated with counting statistics and source orientations. From the data to be collected, especially the unique 37 micron imaging reveals thermal emission from outflow cavities and the relative fluxes from the near and far-facing sides, as a function of wavelength, probes the amount of dense gas in the immediate vicinity of the protostar. Core Accretion models generally involve larger quantities of such gas than Competitive Accretion models. We will compare observational results against specific predictions of a suite of radiative transfer simulations developed by our team to make quantitative tests of the models. We also propose this project as a Thesis Enabling Program, leading to the education and training of Ph.D. student Ms. Mengyao Liu.
Proposal ID: 06_0059
Principal Investigator: Marc Pound (University of Maryland)
Title: Polarized Dust Emission in the Eagle Nebula Pillars
Abstract: We propose the measure the magnetic field morphology in the Eagle Nebula pillars using HAWC+ to map total and polarized dust emission at 89, 154, and 214 microns. We will couple these new measurements with existing measurements of CO, CS, HCN, HCO+, and N2H+ to compare with our simulations of pillar formation in the presence of magnetic fields. These simulations provide projected column density maps, position-velocity diagrams, and plane-of-sky magnetic field maps for a variety of field configurations and strengths. With such analysis we can not only infer the most probable three-dimensional B-field morphology, but estimate its strength without recourse to observationally expensive Zeeman measurements. This would represent the first time magnetic field measurements have been made in any molecular pillar system and provide insight on the importance of magnetic fields in the stellar feedback process in star-forming molecular clouds.
Proposal ID: 06_0061
Principal Investigator: Naseem Rangwala (NASA Ames Research Center/BAERI)
Title: Targeted Extension of the EXES Molecular Line Survey Towards Orion IRc2
Abstract: High spectral resolution molecular line surveys provide a chemical inventory for star forming regions and are essential for studying their chemistry, kinematics and physical conditions. Mid-Infrared (MIR) observations are the only way to study symmetric molecules that have no dipole moment. Previous surveys have been limited to radio, sub-mm and FIR wavelengths. MIR missions such as ISO and Spitzer had low to moderate resolving power that were only able to link broad features with particular molecular bands and could not resolve the individual rovibrational transitions needed to identify specific molecules with certainty. The EXES instrument is currently the only available (airborne or spaceborne) spectrograph that provides high spectral resolution in the MIR region. We have an ongoing, large, EXES program to conduct an unbiased molecular line survey towards Orion IRc2 from 12.5 - 28.5 micron to probe the chemical composition of the Orion hot core. We propose a targeted approach to extend the approved Orion line survey to shorter wavelengths (7.56-7.92 microns), a region strategically selected to maximize the number of interesting, complementary molecular detections. We expect to resolve the rovibrational transitions of at least 8 molecular species. There is a high chance of detecting H2O2 - a key molecule in water and oxygen chemistry in addition to sulphur and nitrogen bearing species, such as CS and N2O. The proposed observations will provide independent estimation of the 12C/13C isotopic ratio and the ortho-to-para ratio behavior in shocked gas. These observations, combined with our existing line survey, will resolve previously detected molecular bands by ISO into lines, measure their rovibrational spectra, and kinematics, and detect new molecules. The measured abundances will be compared with the 12.5 - 28.5 micron survey and the models of hot core and shock induced chemistry.
Proposal ID: 06_0062
Principal Investigator: Joel Green (Space Telescope Science Institute)
Title: Does an FU Orionis Outburst Leave a Lasting Impact on its Circumstellar Disk?
Abstract: The accretion process in protoplanetary disks following a large scale rare outburst such as an FU Orionis object (hereafter, FUor), which superheats the surrounding circumstellar disk in a young stellar system, will determine the materials available for planet formation. The constituents of the protoplanetary disk are tracked in the mid-IR, via continuum, dust features, and ice features, as they are altered in real time by the century-long outburst and aftermath. There is no better option to study disk processing histories than to witness these changes as they occur, particularly if FUor-type events are common (or even repeated) in young disk systems, using the long time baseline allowed by comparing Spitzer-IRS (ca. 2004) and new SOFIA/FORCAST spectroscopy of an FUor bright enough to detect changes. We observed differential cooling or accretion across the disk of FU Orionis in our Cycle 4 program; we propose to conduct this experiment on the more embedded, more rapidly declining V1057 Cyg, V1515 Cyg, and V1735 Cyg.
Proposal ID: 06_0066
Principal Investigator: Enrique Lopez-Rodriguez (SOFIA Science Center)
Title: Characterizing the turn-over of the clumpy torus in active galaxies with HAWC+
Abstract: The reprocessed emission of the active active galactic nuclei (AGN), which emerges predominantly at infrared (IR) wavelengths, reveals both the structure of the immediate AGN surroundings and characteristics of the AGN itself. Probing this key wavelength regime, SOFIA has been crucial in advancing our understanding of the obscuring dusty “torus” and the AGN central engine. However, several important questions still need to be answered: a) How do the properties, such as torus geometry and distribution of clumps, of the torus depend on the AGN luminosity and/or activity class?, b) At which wavelength does the turn-over of the SED occur?, and c) Does the turn-over depends on luminosity and/or activity class?. Thus, a large AGN sample and longer wavelength coverage to obtain statistically significant trends in torus properties is needed. The shape of the spectral energy distribution (SED) reveals the physical distribution of material around the central engine, and the long-wavelength turnover of the SED is particularly sensitive to the total torus extent. Specifically, our pilot study of NGC 1068 using FORCAST and HAWC+ data have observed, for the first time, the turn-over of the torus emission at wavelengths longer than 32 µm. This is only possible by the combination of these two instruments and the angular resolution provided by SOFIA in the 30-90 µm wavelength range. From our study of 13 Seyfert galaxies observed during SOFIA Cycle 2 and 4, our team found that, and against all theoretical predictions, the turn-over of the dust emission from the torus do not occurs up to 37.1 μm. Our study with NGC 1068 found that by observationally constraining the turn-over of the torus emission, the torus is larger by a 30% in size. As we have already exploited the 30-40 μm wavelength range using FORCAST and we observationally have found the turn-over of NGC 1068, we are requesting snapshots at 53 μm and 90 μm with HAWC+ to observationally obtain and characterize the turn-over of 13 AGN. The requested observations will be combined with already acquired 1-40 µm imaging and spectroscopic observations to fit the clumpy torus models. The results of this project will allow us to put tight constraints on the physical scales and geometry of the torus in Seyfert galaxies.
Proposal ID: 06_0071
Principal Investigator: Jonathan Tan (University of Florida)
Title: Joint Impact Program: The Timescale of Star Formation from para-H2D+ - II. Colder and Lower Luminosity Sources
Abstract: The timescale of star formation is of fundamental astrophysical importance, but is currently very uncertain. The SOFIA discovery of para-H2D+ in the accretion envelope of a forming Sun-like star (Brunken et al. 2014, Nature, 516, 219) and the fact that the ortho-to-para ratio (OPR) of H2D+ can be used as a proxy of the OPR of H2, which is the best chemical clock of molecular clouds, enabled an age estimate of >1Myr. This ground-breaking result has motivated this Joint Impact Program, approved in a pilot phase in Cycle 4, to extend such studies throughout the Galaxy. The program aims to measure para-H2D+ with GREAT at 1.37 THz in absorption toward a large sample of high- & intermediate-mass protostars. Lines of sight to these sources probe protostellar/protocluster envelopes in a variety of environments relevant to the bulk of star formation in the Milky Way. These protostars are already the subject of SOFIA-FORCAST observations, which, combined with radiative transfer modeling, enable estimation of envelope density & temperature profiles needed for the astrochemical analysis to derive ages. The para-H2D+ absorption line data will then be utilized together with observations of ground state ortho-H2D+ to measure OPR of H2D+ and thus, in comparison with astrochemical models, the OPR of H2. Measurement of OPR of H2 allows estimation of the age of the molecular gas, i.e., the time since the H2 formed from HI. We will thus measure for the first time the ages of a statistically significant sample of star-forming molecular clouds and put stringent constraints on theories of the dynamics of star & star cluster formation. Here in Cycle 6, guided by preliminary results from our Cycle 4 observations of several luminous protostars in the sample, we next focus on colder, lower luminosity sources.
Proposal ID: 06_0072
Principal Investigator: Ryan Lau (Caltech)
Title: Investigating the Massive Star Formation Region Sh2-209 in the Extreme Outer Galaxy
Abstract: The Extreme Outer Galaxy (EOG) is the largely unexplored region beyond a Galactic radius of 18 kpc that hosts a low metallicity and low density environment. The EOG therefore provides a unique laboratory to study star formation in conditions similar to the early epochs of our Galaxy’s formation and galaxies in the early Universe. Surprisingly, the EOG hosts regions of young and massive star formation, which raises the question: what triggers star formation in the EOG and what are the properties of the resulting star formation? Sh2-209 is the largest site of massive star formation in the EOG that hosts a ~0.5-1 Myr-old stellar cluster surrounded by a ~9 pc shell where triggered star formation may be occurring. Sh2-209 is therefore the ideal site to investigate star formation in the EOG. We propose SOFIA/FORCAST imaging observations at 19, 25, 31, and 37 µm to obtain high spatial resolution (~3” FWHM) maps of warm dust emission from Sh2-209. Our goal will be to search for young stellar objects as evidence of triggered star formation in Sh2-209 and to measure star formation rates to compare with other Galactic environments. Our observations will also provide dust mass estimates to determine the gas-to-dust ratio of the interstellar medium in the EOG. With this information, we can investigate the expansion timescales of the Sh2-209 HII region and test the hypothesis of star formation triggered by feedback from the central cluster. The proposed SOFIA/FORCAST observations of Sh2-209 will complement our JWST GTO program studying distant, fainter, and less massive EOG star formation regions. Sh2-209 is ideal for SOFIA/FORCAST due to its high surface brightness and extended size. Observations of Sh2-209 are also not feasible with JWST due to saturation. We request 3.6 hr of total observing time with SOFIA/FORCAST to perform this study. The anticipated results will highlight SOFIA as an ideal platform for studying star formation in unique Galactic environments.
Proposal ID: 06_0074
Principal Investigator: James Jackson (Boston University)
Title: [C II] Emission from High-Mass Star-Forming Clumps
Abstract: The [C II] 158 µm line is the single brightest spectral line from star-forming galaxies and is often used to characterize their global star-formation rates, especially at high redshifts, where its enormous luminosity allows it to be detected. Presumably the extragalactic emission arises from thousands of dense, high-mass star-forming molecular clumps blended together in the kpc-scale telescope beam. Despite its common use as an extragalactic star-formation tracer, there have been no large, systematic studies to characterize the [C II] behavior in individual clumps in the Milky Way, where the detailed nature of the clump properties and their embedded young stars and protostars can be accurately measured. We have recently completed the MALT90 catalog of ~3,000 high-mass star-forming clumps that we have thoroughly characterized in their far-infrared, submillimeter, and millimeter gas and dust properties, including photometric and spectroscopic analyses and a determination of their kinematic distances. Previous SOFIA/FIFI-LS images of 4 clumps shows an enormous variation (more than a factor of 70) in the [C II] to continuum flux ratio. To build on this work, we have carefully selected a subsample of 50 luminous, compact, UV emitting clumps whose PACS 160 µm fluxes suggest good S/N detections of the [C II] line in 37 minute, fully-sampled, 2'x2' maps. The subsample spans a range of 100 in luminosity. This SOFIA program will enable us to calibrate and study how the [C II] emission correlates with these star-formation properties, and will lead to better understanding of the global [C II] properties of luminous infrared galaxes, especially the "[C II] deficit" problem.
Principal Investigator: Stefan Heese (Institut fuer Theoretische Physik und Astrophysik der Universität Kiel)
Title: Bok globules in the infrared: Are polarization holes caused by optical depth?
Abstract: Polarimetric observations of Bok globules frequently show a decrease in the degree of polarization towards their central dense regions (polarization holes, Henning et al. 2001; Vallee et al. 2003; Wolf et al. 2003). This behavior can be explained with multiple physical conditions and effects (Brauer et al. 2016). For instance, a high optical depth in the core of Bok globules is expected to significantly reduce the degree of polarization. However, the relative importance of these effects has not been confirmed quantitatively. We will investigate the influence of the optical depth on the occurrence of polarization holes in observations of Bok globules at 850 microns. We make use of HAWC+ polarimetric observations at 154 microns (D) and 214 microns (E) to obtain the orientation and degree of linear polarization in the central regions of the ok globules CB54 and CB68. Compared to each other and observations at 850 microns, the relative importance of the optical depth effect can be estimated. We expect to obtain the Stokes parameter I, Q and U of the central regions of the Bok globules CB54 and CB68 to calculate the orientation and degree of the linear polarization.
Principal Investigator: Cristian Guevara (I. Physikalisches Institut - Uni zu Koeln)
Title: [CII] M17SW and X-rays emission
Abstract: Our recent observations with SOFIA/upGREAT at very high velocity resolution and S/N have shown for a number of source, M17SW being the one with the most prominent features, that the [Cii] line has an unexpected high opacity and is heavily affected by self-absorption. Both the high column densities of the warm emitting gas (presumably due to a much larger number of PDR layers than usually expected), but in particular the large opacity, and therefore column density, of the cool foreground absorption gas, are very hard to explain in the context of standards models to explain the [CII] emission, i.e. in the PDR model scenario. In this scenario, C+ is formed only in regions of elevated temperatures and it is basically impossible to get large columns of cool C+ gas. The alternative of subthermal excitation of the [CII] line can also be rules out, because the extend of the individual absorption features together with the column density of the absorbing material results in densities that are at least of the order of the critical density of the [CII] line. One possibility to explain the large columns of cool C+ gas is, that an elevated X-ray flux leads to unusually high ionization levels of carbon also in the cool interiors of clumps, resulting in the observed deep absorption notches. M17SW is a giant molecular cloud located at 1.98 kpc, and it is illuminated by a cluster of OB stars at 1 pc to the east. It is one of the best galactic regions to study PDR structure from the exciting source to ionization source. The structure is highly clumpy from several studies of molecular emission. With this proposal, we want to test the hypothesis of enhanced X-ray flux explaining the high columns of cool C+ gas by observing a recently identified molecular condensation apparently associated with a prominent X-ray source cluster locate slightly in front of the “standard” M17 SW PDR interface region.
Principal Investigator: Victor Doroshenko (IAAT; Universität Tübingen)
Title: The shell in the shell: dust in TeV SNR HESS J1731-347
Abstract: Cosmic dust is an important ingredient of the Galactic evolution, and one of the main observational probes to study the star formation processes. Significant fraction of dust is believed to be produced in atmospheres of evolved stars and supernova ejecta, yet the details are unclear. Here we propose to observe a unique, recently discovered, dust shell around a post-AGB star located in the centre of a young TeV emitting supernova remnant HESS J1731-347. The massive dust shell is heated by the central post-AGB star located in the immediate vicinity of the centre of the remnant and the central neutron star. Most of the observed dust is clearly associated with supernova ejecta, yet the shell seems to be shaped by the wind of the central star. Using the multi-band SOFIA/FORCAST imaging we will investigate the details of this interaction through mapping of spatial and temperature structure of the shell, constrain basic dust parameters and luminosity of the central star, estimate the total dust mass and the contribution of the post-AGB star to the total dust budget. The propsed investigation is highly synergic to studies of the remnant in radio, X-ray and TeV bands and will be used to aid these investigation through getting better understanding of the conditions within the remnant and independent estimate of the distance to the source.
Proposal ID: 06_0085
Principal Investigator: Shohei Aoki (Institut d'Aeronomie Spatiale de Belgique)
Title: Mapping of HDO/H2O and CH4 on Mars using SOFIA/EXES: Joint observations with ExoMars Trace Gas Orbiter
Abstract: Studying the Martian atmosphere provides important information regarding past and present likelihood of life existing on Mars. Mapping the HDO/H2O ratio on Mars is a key diagnostic for understanding the past history of water and better understanding the water cycle. However, its seasonal and spatial variation are poorly understood. SOFIA, above over 99% of the terrestrial water vapor, allows us to observe H2O and HDO transitions simultaneously, and thus to retrieve the HDO/H2O ratio with maximum reliability. We have performed a sensitive mapping of HDO/H2O by using SOFIA/EXES during an EXES commissioning flight and Cycle 4. Here, we propose to complete our seasonal coverage by adding 3 new measurements during Cycle 6. Discovery of CH4 in the Martian atmosphere has led to much discussion since it could be a signature of on-going/past biological or geological activities on Mars. However, its global distribution to identify a source is still unknown. SOFIA enables us to significantly reduce the effects of terrestrial atmosphere and improve the chance to detect tiny Martian CH4 lines. We have performed a sensitive search of CH4 by using SOFIA/EXES during Cycle 4, however our results show that there are no definitive detections of CH4. Here, we propose to continue the sensitive search of CH4 on Mars. To increase the chance to detect CH4, we propose to have observations during the seasonal period that Curiosity/TLS detected CH4 over Gale Crater. Last but not least, this is an unique opportunity to perform joint observations with ExoMars Trace Gas Orbiter (TGO), expected to start the science operation in April 2018. Instruments onboard TGO are optimized for solar occultation measurements, which provide sensitive investigation of the vertical profiles, while SOFIA/EXES enables us to obtain global snapshots. Our coordinated observations will provide complementary information of HDO/H2O and CH4 on Mars.
Principal Investigator: Elena Redaelli (Max Planck Institute for Extraterrestrial Physics)
Title: Polarimetry in B228
Abstract: Polarimetric observations are an essential technique to observe and understand the role of the magnetic fields during the star formation process at core scales (0.1 pc). With the SOFIA/HAWC+ instrument, we can achieve high angular resolution investigations in nearby star forming regions. We propose to perform polarimetric observations in band E toward Barnard 228, a Class 0 young stellar object (YSO) situated in the Lupus I molecular cloud. The diffuse gas surrounding this object is threaded by a very ordered magnetic field. The HAWC+ spatial resolution at the B228 distance is approximately 0.01 pc, enough to resolve substructures on the magnetic field, especially if the small-scale fields have a significant turbulent component. The source has bright emission at 250 micron, as seen in Herschel/SPIRE map, and it is connected to a small filamentary structure seen in dust. For these reasons, this object is an ideal target for HAWC+ observations. The polarization will allow us to link the core-scale magnetic properties with the cloud-scale ones, casting light on how magnetized clouds evolve to form prostostellar objects. We will observe how the polarization is oriented with respect to the dust emission, helping us to understand if the B-field dominates the core dynamics by shaping the cloud structure. We will also observe if such a field is affected by the protostellar feedback. We are preparing a follow up proposal for molecular line observations in order to unveil the kinematics of the source, looking for signs of correlation between the velocity field and the polarization structure.
Principal Investigator: Felipe Alves (Max-Planck-Institut für Extraterrestrische Physik)
Title: THz polarization from cores at distinct evolutionary stages
Abstract: Linear polarization observations reveal the morphology of the magnetic field in star-forming regions. However, polarization observations at ~pc scales are still rare, despite of their importance in the framework of magnetized cloud evolution. In this sense, SOFIA/HAWC+ is a unique instrument for observing the extended polarized flux in molecular cores. We propose 1.4 THz polarization observations toward two regions at distinct evolutionary states: the prestellar, starless core FeSt 1-457, and the active core B59. Both objects are located in the magnetized Pipe nebula, at a distance of 145 pc. B59 has bright 250 micron (Herschel/SPIRE) emission peaking at the Young Stellar Objects embedded in it, while FeSt 1-457 has a centrally peaked emission. These observations will reveal the magnetic field from scales of 0.3 pc down to 0.01 pc, the HAWC+ spatial resolution at the Pipe distance. Our goal is to compare the HAWC+ polarization with previous optical and near infrared polarization data from the core surrounding, diffuse gas (for B59 and FeSt 1-457) and submm polarization data from the core densest parts (for FeSt 1-457) at similar spatial scales. For B59, we will be able to investigate if the magnetic field is preventing the core to undergo further fragmentation, while for FeSt 1-457 we will observe the magnetic field at distinct volume density regimes. We will also compare dust properties such as alignment efficiency at a quiescent and active environemtn. Finally, we will complement this study with molecular line data, that will reveal how the core kinematics compares with the magnetic field morphology.
Proposal ID: 06_0088
Principal Investigator: Paul Goldsmith (JPL, NASA)
Title: Observing Polarization and the Magnetic Field of Star-Forming Filaments in Serpens South
Abstract: We propose to observe polarization and magnetic fields in Serpens South, stellar-cluster-forming filaments, using the HAWC+ on SOFIA. Molecular filaments are common structures within molecular clouds, and recent observations using infrared and radio telescopes such as Spitzer Space Telescope, Herschel Space Observatory, ALMA, GBT, etc. have revealed that filamentary star formation is a dominant mode of star formation in our Milky Way. Thus, understanding physical and chemical processes within molecular filaments has been a crucial key to deciphering star formation processes, and many observational and theoretical projects are currently active to pursue the answers. However, magnetic fields, which play a critical role in star formation, are often neglected in those filament studies due to difficulties in observing magnetic fields directly. SOFIA now has HAWC+, a highly sensitive infrared camera and polarimetry, which are capable of mapping polarization of star-forming regions with unprecedented speed and spatial resolution in far-infrared. In this project, we aim to map polarization and magnetic fields of the entire structures of Serpens South using HAWC+ at Band E in 14 hours. Serpens South is a prominent star-forming region which consists of a hub radiating two large filaments, a protostellar-cluster at the hub, and numerous protostars in filaments. A deep and high-resolution observation will certainly provide answers to the role of magnetic fields in filamentary star formation and various physical processes related magnetic fields. This project will have an enormous impact on understanding star formation in our Milky Way and an excellent showcase of SOFIA HAWC+ to the scientific community as well as general public.
Proposal ID: 06_0089
Principal Investigator: Roberta Humphreys (University of Minnesota)
Title: The Mass Loss Histories of the Red Supergiants
Abstract: The evolution and final fate of stars in the 9 to 30 solar mass range as red supergiants (RSGs) and ultimately as SNe, has long been considered to be well understood. The majority of massive stars will pass through the RSG stage, but recent studies suggest that those RSGs above 18 solar masses may not terminate as SNe. The RSG stage is a high mass-losing stage, but to what extent mass loss and their mass loss histories affect their terminal state is now an open question. We propose to long-wavelength imaging with FORCAST of a coeval population of RSGs to explore their mass loss histories. We have selected two clusters with remarkably large populations of evolved stars including numerous RSGs. They are an ideal population for comparing the stars' mass loss histories with their derived parameters such as luminosity, spectral type, and initial mass at a fixed age and in a known environment. We have obtained near-IR AO imaging with LBT/LMIRCam of several stars in these clusters and time has been granted with VLT/NACO for near-IR imaging polarimetry. The addition of mid-infrared photometry with FORCAST will measure the thermal emission for the cool dust which may be a record of earlier mass loss. The long wavelengths are critical for modeling the SEDs. The models provide constraints on the properties of the circumstellar dust, and variation in the dust density distribution yields information on the mass-loss history. In combination with the near-infrared imaging, we can reconstruct their mass loss histories over 100s to thousands of years.
Proposal ID: 06_0090
Principal Investigator: Brett McGuire (National Radio Astronomy Observatory)
Title: A SOFIA Survey of Interstellar Hydrides
Abstract: Hydrides (XH) are common in the interstellar medium (ISM), with detections of H2, CH, NH, OH, HF, SH, HCl, and potentially SiH. These molecules are key progenitors of more complex organic molecules that are the subject of intense study in star and planet- formation, and are also used as probes of the reservoir of X available to undergo chemistry. Thus, it is critical to either observe, or stringently quantify, these hydrides. This is particularly true for species for which X is seen in more complex species, but for which no XH detection exists. Here, we propose a search for strong transitions of PH and FeH with SOFIA GREAT to detect these for the first time, and transitions of SiH to confirm this long-tentative ISM detection. We will integrate on each molecule toward either the C-rich IRC+10216 or the O-rich VY Canis Majoris, or both, depending on the specific chemical conditions in each source with respect to the individual hydride. The derived detected abundances, or stringent upper limits, will provide invaluable information both on the extent of X fixed in these hydrides, and their availability (or lack thereof) as progenitors of more complex species.
Proposal ID: 06_0091
Principal Investigator: Graham Harper (University of Colorado Boulder)
Title: Probing the near-stellar environments of core-collapse supernova progenitors with upGREAT
Abstract: When the shockwave from a core-collapse supernova emerges through the progenitor's photosphere it enters into the poorly understood extended atmosphere where the original stellar outflow was being accelerated. The gas density in this zone has an impact on the interpretation of early-time spectra that are now being collected thanks to the new fast response of transient surveys. We therefore propose to use upGREAT to spectrally resolve [O I] 63.2 micron and [C II] 157.7 micron emission profiles to probe this important region for a small sample of red supergiants to constrain the symmetry and structure of their outflows. We will combine these spectra with supporting observations to construct semi-empirical models which can be used to constrain mass loss theories and aid in the interpretation of early-time supernova spectra.
Proposal ID: 06_0093
Principal Investigator: Kenneth Hinkle (NOAO)
Title: Measuring water in the AGB circumstellar outflow
Abstract: Many gaps remain in our understanding of mass loss on the AGB. The AGB Mira stage of low mass stars accounts for 90 percent of the mass loss in these stars. The cool outflow from Miras is molecular and low excitation lines are formed through the molecular envelope into the circumstellar gas expanding at terminal velocity. For oxygen-rich stars H2O could be one of the most useful molecular probes. However, H2O is very difficult to use because the telluric H20 spectrum is opaque for the most significant astrophysical transitions. Science verification observations with SOFIA demonstrated the ability of EXES to observe the lowest excitation transitions of the strongest of the H2O vibration-rotation bands, the 6 micron (010)-(000) bending transition. We propose a first application of these lines to AGB stars to measure the acceleration of circumstellar gas and the abundance of water in the gas as it passes from the base of the circumstellar shell to the H2O maser region. These parameters will provide vital information on the role of grain mantels in transforming transparent grains into grains that can be pushed by radiation pressure.
Proposal ID: 06_0094
Principal Investigator: Robert Gehrz (University of Minnesota - Twin Cities)
Title: SOFIA Target of Opportunity (ToO) Observations of Bright Classical Novae in Outburst Abstract:
Abstract: Classical novae (CNe) contribute to Galactic chemical evolution by injecting dust grains and gases into the interstellar medium (ISM). We have conducted SOFIA Cycle 1, 2, 3, and 4 FORCAST and FLITECAM Target of Opportunity (ToO) grism observations of the temporal development of bright CNe. Here, we propose to extend our program into Cycle 6 with FORCAST to cover the continued development of CNe that became active during Cycle 5 and to initiate coverage of CNe that go into outburst during Cycle 6. The proposed observations can determine critical physical parameters that characterize the explosion and CNe contributions to the ISM. Our observations will yield the mass ejected, the mineralogy and abundance of the dust grains, and gas phase abundances of CNONeMgAl metals in the ejecta. The 5 to 37 micron spectral range of FORCAST grisms enables complete and simultaneous access to the many dust and gas emission features. Any new nova brighter than 8th magnitude at visual maximum can trigger our ToO program when supporting optical/IR ground-based observations indicate that the nova is in 1) a dust formation and growth phase, 2) a forbidden line emission development phase, or 3) the early free-free expansion phase. The timescales for SOFIA ToO follow-up observations for a nova that triggers our ToO program can range from weeks, months, and years for cases 1) and 2), to days and weeks for case 3).
Proposal ID: 06_0095
Principal Investigator: Aneurin Evans (Keele University)
Title: Quest for the Ring: is there benzyne in Sakurai's Object?
Abstract: We propose to observe Sakurai's Object (V4334 Sgr) in the 18 micron region using EXES. Our aim is to confirm the tentative detection of benzyne in our previous observations of Sakurai's Object with FORCAST. The confirmation of benzyne would impact strongly on our understanding of how the basic molecules of life form in circumstellar environments.
Proposal ID: 06_0096
Principal Investigator: Aneurin Evans (Keele University)
Title: Exploring the environments of recurrent novae between eruptions
Abstract: We will obtain FORCAST grism and imaging observations of three recurrent novae having long orbital periods. The secondary star in these systems is a red giant with a substantial wind, and when the nova erupts the ejected material runs into the wind and shocks it. This results in coronal emission in the infrared, non-thermal radio emission, and X-ray and gamma ray emission. Understanding recurrent nova systems in quiescence is important to understand the progress of the nova explosion, and will throw light on the newly-discovered phenomenon of gamma ray emission in classical novae.
Proposal ID: 06_0097
Principal Investigator: Leslie Looney (University of Illinois)
Title: Feedback in the Massive Protocluster Environment of W43-Main
Abstract: Massive stars play a fundamental role in galactic evolution at all stages of their relatively short lives, especially influencing the molecular clouds in which they form. In addition, massive star formation typically occurs in large star forming regions or clusters, which makes observations of these systems more complex and makes feedback and interactions more important. W43 is considered by many as the most active star forming region in our Galaxy and more similar to star formation in starburst galaxies, which makes it an ideal location to study massive star formation and feedback from a co-spatial HII region. Although we have nice [CII] maps from our Cycle 4 observations, we are missing (1) observations of the peak caused by the cluster powering the HII region, (2) deeper [CII] observations toward the MM1 ridge, and (3) the important diagnostic line pair of [OI] at 63 and 145 microns. With these we will constrain the physical conditions of the cloud environment in the W43 main region (i.e., density, temperature, and radiation field) and reveal the properties of the W43 MM1 ridge and M43-main cloud, as well as the effect of the HII region on the cloud. With these observations, we will probe the conditions around the ridge, as well as the interaction with the HII region, which will provide useful inputs into theoretical descriptions of the star formation process in this cloud and make important constraints on the details of massive star formation in such clusters.
Proposal ID: 06_0098
Principal Investigator: Ian Stephens (Smithsonian Astrophysical Observatory)
Title: The Role of Magnetic Fields in a Filamentary Low-mass Star-Forming Region
Abstract: The magnetic field morphology at scales between a few thousand AU and a few tenths of a parsec is poorly constrained. However, knowing the field at these scales is very important since magnetic fields can shape filaments (~0.1 pc scale) and influence the fragmentation and stellar evolution of protostars. We select one of the best studied star forming regions, NGC 1333 in the Perseus molecular cloud, to survey with the HAWC+ polarimeter at 214 µm. These observations will detect polarization in a couple thousand independent beams throughout the filamentary complex of NGC 1333. From these observations, we will investigate the field morphology of filaments, test filamentary models, and show how fields at this scale play a role in protostellar evolution, multiplicity, and disk formation. To determine the relative importance of magnetic fields, turbulence, outflows, and gravity, we will calculate the energy density of each, and compare the multi-scale magnetic field to state-of-the-art MHD simulations.
Proposal ID: 06_0099
Principal Investigator: Fabio Santos (Northwestern University)
Title: Magnetic Field Structure in Perseus at 0.01 pc Scale
Abstract: The ion-neutral decoupling scale is one of the fundamental quantities governing the physics of the star formation process. For a weakly ionized gas, such as that encountered in star-forming regions, this scale corresponds to the smallest scale at which the magnetic field is frozen to the mostly-neutral gas. Beneath this scale, turbulence in the magnetic field will be significantly damped and MHD waves will be unable to propagate. Although some observational evidence has been obtained for this diffusion scale, all consistent with expectations from theoretical and simulation studies, a direct and definitive detection has yet to be realized. We thus propose to use the newly commissioned HAWC+ polarimeter on SOFIA to perform observations at high sensitivity and angular resolution on three distinct regions in the nearby Perseus molecular cloud. These measurements in the C, D, and E bands will allow the detection of several hundred polarization vectors at resolutions of, respectively, 11 mpc, 20 mpc, and 27 mpc at the distance of Perseus. We will then be able to resolve the expected ion-neutral decoupling at the expected scale (around 45 mpc) for the densities probed by our observations (approximately 10000 particles per cubic cm). Analyses of these data using state-of-the-art methods (e.g., the angular dispersion and the Histograms of Relative Orientations methods) will allow us to characterize the turbulence power spectrum and provide the magnetic field information necessary to test the results and predictions from both numerical simulations and analytical studies.
Proposal ID: 06_0100
Principal Investigator: Kathleen Kraemer (Boston College)
Title: Real-Time Evolution of Carbon-Rich Post-Asymptotic Giant Branch Stars
Abstract: We propose to observe a set of carbon-rich post-asymptotic giant branch (post-AGB) stars with the FORCAST grisms. With SOFIA, we can, for the first time, spectroscopically investigate the changes that occur in the circumstellar envelopes during this short-lived phase of stellar evolution, as these objects transition from AGB stars with dense circumstellar envelopes to planetary nebulae (PNe) characterized by extended, diffuse clouds of hot gas and dust. Our targets consist of carbon-rich post-AGB stars which were observed with the Short-Wavelength Spectrometer on ISO almost 20 years ago, and most also have spectra from IRAS, increasing our temporal baseline to 35 years and increasing our likelihood of detecting the transitions we know are taking place. Secular changes on these timescales have already been detected in optical photometry and spectra, tracing changes in the central star. We are now in a position to observe the corresponding changes in their circumstellar material, as it is being processed from forms found around AGB stars to those seen in PNe. The new FORCAST spectra will allow us to probe the near real-time evolution of these circumstellar shells. We request 4.9 hours to complete this project.
Principal Investigator: Timea Csengeri (Max Planck Institute for Radioastronomy)
Title: Constraining the oxygen budget in the diffuse and dense gas towards the Galactic mini-starburst, W51 Main
Abstract: Radiative feedback from massive stars greatly impacts the evolution of the interstellar medium. In particular, Galactic mini-starburst regions, undergoing a very active phase of star formation, serve as excellent laboratories to study the heating and cooling processes due to the intense UV field imposed both locally from the young stars, and externally from the previous generation of massive stars. In a comprehensive study, we used SOFIA/GREAT [CII] observations complemented with ground-based [CI], and CO data to characterise the cooling towards the well known mini-starburst region, W51 Main. While our results show that [CII] is a secondary contributor to the total line cooling, we lack the contribution of [OI] to the cooling budget, which is predicted to be important based on Herschel studies. Here we propose therefore to use the high spectral resolution fast mapping capabilities of the GREAT LFA/HFA receiver in order to obtain a complete view on the two atomic fine structure lines of oxygen at 145, and 63 microns. Our first goal is to complement our assessment of the cooling budget including the [OI] line, and compare it with low spectral resolution Herschel/PACS based studies. These show that [OI] typically contributes up to 35%, however, in some cases it reaches up to 80%. Interestingly the cooling in (U)LIRGS shows a very different picture, where [CII] and [OI] are the primary coolants of the gas. We will therefore particularly focus on comparing the far infrared cooling also towards the diffuse gas component, and externally illuminated PDR surfaces covered in this region. Our second goal is to constrain the physical conditions of the diffuse and dense gas components using the line ratio of the two [OI] transitions, but also to use the [CII] and [OI] line ratios to constrain the PDR models towards the dense PDR shell associated with the W51e source in this region. Our third goal is to complement the Herschel/WISH H2O observations towards this region, combined with the [OI] and CO data we will be able to constrain the total budget of volatile oxygen in this region.
Proposal ID: 06_0104
Principal Investigator: Yao-Lun Yang (The University of Texas at Austin)
Title: Exploring Protostellar Winds with [OI]: Constraining models of shocked gas and PDR using L1551-IRS5
Abstract: The formation of stars and planets requires a transfer of angular momentum by fast (v ~ 100 km/s) winds. The role of winds in dispersal of circumstellar envelopes of embedded protostars controlling the mass of the star/disk system, and in distributing dust in the disk (which is often already sedimented by the late protostar phase), is poorly understood but crucial to models of accretion and planet formation. Winds are seen only indirectly as the swept-up gas forms a molecular outflow with velocities of a few to 10s of km/s. Direct observation of winds from embedded protostars is difficult because the atomic lines that trace the particle flux are typically emitted at optical/UV wavelengths, where they are attenuated by the enveloping dust. The [OI] 63µm fine structure emission line, the dominant coolant in shocked gas, should be an excellent tracer of the wind flux. Neutral oxygen should be produced in the shocked wind and [OI] provides a direct measure of the mass loss rate in the wind. However, photodissociation regions, where the UV flux from the star/disk system interacts with the outflow cavity wall, also produce [OI] and [CII] 158µm. In order to properly estimate the mass loss rate, we require velocity-resolved line profiles to separate the contribution of PDRs from shocks. Shocked gas should be offset, while the gas in PDR will be close to the sound speed. We propose to use SOFIA-GREAT to answer the question: What are the properties of the shocks emitting the observed [OI] and [CII] lines? We will use the high spectral resolution of GREAT to measure the line profiles toward an embedded protostar, which shows features of strong shocks and is less affected by interstellar radiation: the well-characterized protostar L1551-IRS5 provides an ideal test environment.
Proposal ID: 06_0107
Principal Investigator: Michael McCarthy (Harvard-Smithsonian Center for Astrophysics)
Title: Searching for the missing sulfur: new candidates for molecular sinks
Abstract: A long standing problem in astrochemistry is the inability of current models to account for missing sulfur content. While the abundance of sulfur in the diffuse interstellar medium is comparable to that of stellar environments, the same cannot be said for dense regions, where sulfur is depleted by several orders of magnitude. This apparent anomaly has led to speculation as to where the missing sulfur is sequestered: on dust grains, in unconsidered locations/states, or trapped in currently unknown gas-phase molecules that act as thermodynamic sinks for sulfur content in these regions. To test the hypothesis that molecules might be significant sulfur reservoirs, we have recently identified several new S-bearing species of astronomical interest in our laboratory, and precisely characterized their rotational spectra. SOFIA is ideally suited to detection them in astrophysical sources. We will detect, or provide rigorous upper limits for neutral HSCCH, and two positive ions, HSCS+ and HSCO+, in two distinct environments: the cool (complex) molecular shell surrounding Sgr B2(N) and the diffuse and translucent molecular clouds which lie along the line-of-sight. The results will determine whether these species are substantial reservoirs of sulfur, and will provide critical constraints for chemical models that attempt, but currently fail, to address this important issue. We will use the GREAT instrument on SOFIA to observe several high-frequency transitions of each species. From simulated rotational spectra, which are based on very precise laboratory rest frequencies and/or high-level ab initio calculations, the strongest transitions for each lie in the frequency range of the L#1 detector (1250 - 1500 GHz), with a window coverage of 420km/s. The windows will be selected to observe both the Sgr B2 complex, and the line-of-sight clouds. At one hour of observation per molecule, we will achieve an order of magnitude improvement relative to existing upper limits.
Proposal ID: 06_0109
Principal Investigator: Umut Yildiz (Jet Propulsion Laboratory)
Title: Where is the oxygen in protostellar outflows?
Abstract: Oxygen (O) is the third-most abundant element in the Universe after hydrogen and helium. Despite its high elemental abundance, a good picture of where oxygen is located in low-mass protostellar outflows and jets is missing: we cannot account for > 60% of the oxygen budget in these objects. This hole in our picture means that we currently do not have a good understanding of the dominant cooling processes in outflows jets, despite the fact that [O I] emission at 63 micron is one of the dominant cooling lines, nor how cooling processes evolve with protostellar evolution. To shed light on these processes, we propose to observe the [O I] 63 micron line with SOFIA-GREAT toward ten low-mass protostars. As a first step, the velocity-resolved line profile will be decomposed into its constituent components to isolate the relative contributions from the jet and the irradiated outflow. Second, the [O I] line profile will be compared to those of H2O, OH and CO to obtain the relative atomic O abundance with respect to CO, H2O, and OH. Third, the effects of evolution will be examined by observing protostars at different evolutionary stages. These three approaches will allow us to quantify: the oxygen chemistry in warm and hot gas, the relative amounts of material in the outflow and the jet, and finally to start tracing the evolutionary sequence of how feedback evolves with time.
Proposal ID: 06_0111
Principal Investigator: Robert D. Gehrz (Minnesota Institute for Astrophysics, University of Minnesota)
Title: SOFIA Target of Opportunity Observations of Galactic Supernovae and Supernovae in Nearby Galaxies
Abstract: We propose to conduct repeated SOFIA FORCAST grism Target of Opportunity (ToO) observations of Galactic supernovae and supernovae in nearby galaxies that may occur during the SOFIA Cycle 6 observing period. Our FORCAST objectives will require SNe in galaxies less distant than ~1 Mpc distant. The scientific focus of the proposed observations is the determination of the temporal development of the ejecta and the nature of the interaction of the supernova radiation, ejecta, and blast wave both with each other and with the surrounding material.
Proposal ID: 06_0112
Principal Investigator: James Jackson (Boston University)
Title: Infall toward High-Mass Star-forming Clumps and Cores: The [O I] 63 µm Line
Abstract: Although the 63 µm line has often been used as a diagnostic of photodissociation regions, toward cold, dense infrared dark cloud clumps it is often seen in absorption. We aim to exploit this high optical depth in IRDCs to probe the infall velocities and mass accretion rates of high-mass star-forming clumps and cores. We will use "blue asymmetric" self-absorbed line profiles or redshifted absorption against the protostellar dust continuum to measure infall rates. We will target 8 IRDC clumps in NGC6334 and "Nessie" to probe how the infall rates may change with evolutionary stage.
Proposal ID: 06_0116
Principal Investigator: Giles Novak (Northwestern University)
Title: Joint HAWC+/ALMA Study of Young Protostars in Ophiuchus
Abstract: Using ALMA, the superb new international astronomical facility in Chile, astronomers are at the threshold of directly observing the process of planet formation, thereby stimulating intense research activity by theorists and observers worldwide. However, stubborn puzzles remain, including the "magnetic braking catastrophe" which refers to our failure to understand what stops magnetic forces from funneling all disk material directly into the nascent star. Proper tests of theories that address this puzzle will require observations of magnetic fields over a very wide range of spatial scales. The nearby rich stellar nurseries in Ophiuchus, just 125 parsecs away, provide a unique opportunity to carry out such tests. By combining polarimetry data from the Planck satellite, the HAWC+ far-IR polarimeter on SOFIA, and ALMA, we can trace magnetic fields nearly continuously over more than four orders of magnitude in spatial scale. Here we propose to observe eight protostars with HAWC+/SOFIA, out of 17 bright protostellar targets selected via ALMA total intensity mapping and proposed for ALMA polarimetry. Our results will test whether magnetic field misalignment is important for disk formation and allow field strength estimates, both of which are key unknown factors that strongly affect the formation of disks around protostars.
Proposal ID: 06_0117
Principal Investigator: Alexander Tielens (Universiteit Leiden)
Title: EXES Survey of the Organic Inventory of Hot Cores
Abstract: We propose to measure the 5.4-6.4 micron spectrum of the Hot Core associated with the massive protostar AFGL 2136 at high spectral (R=50,000) resolution and high sensitivity (S/N~100) with the goal of determining the organic inventory. These data will be combined with 6.4-8.0 micron EXES and 10-13 micron TEXES/Gemini observations already obtained for this source. We will also propose to complement these data with a TEXES/IRTF or Gemini 8-10 micron spectrum to provide complete coverage from 4.5 to 13 micron. Hot Cores are chemically very diverse as many chemical and physical processes contribute to their molecular content. This spectral region contains the ro-vibrational transitions of many molecules known or expected to be abundant. The absorption line depths and profiles are unique signatures of the absorbing species and the kinematics of the region. The data will be analyzed to determine column densities and abundances relative to CO, as well as the kinematics and the physical conditions in the absorbing gas. Derived abundances can also be directly compared to abundances of interstellar ice components obtained along the same sight-lines. With our study of the Hot Core towards AFGL 2591, these observations will provide an unprecedented data set, offering a unique view of the molecular content and physical conditions in regions of massive star formation and the physical and chemical processes that play a role in the origin and evolution of Hot Cores. In addition, this study will provide a benchmark for the interpretation of much lower spectral resolution studies of Hot Corinos and protoplanetary disks around low mass stars to be obtained with MIRI/JWST.
Proposal ID: 06_0119
Principal Investigator: Ian Stephens (Smithsonian Astrophysical Observatory)
Title: Mapping the Magnetic Fields in Intermediate-Mass Clumps
Abstract: The role of magnetic fields in star-forming clumps are poorly constrained. In particular, field measurements are especially rare in intermediate-mass clumps We will investigate the role of magnetic fields in the intermediate-mass filamentary clumps NGC 2068 and NGC 2071, which are contained within the Orion B Molecular Cloud. These clouds represent a typical mode of Galactic star formation. With 11 pointings, we will detect thermal dust polarization with over 3500 independent vectors. From these observations, we will determine how magnetic fields guide mass through filamentary complexes. NGC 2068 and NGC 2071 are in close proximity to each other, but they have very different masses and star formation activities. Thus, they are ideal targets. We will further investigate how intermediate mass clumps compare to their low-mass and high-mass clump counterparts. Finally, we will combine our data with JCMT to constrain grain alignment via radiative torques.
Proposal ID: 06_0121
Principal Investigator: John Tobin (University of Oklahoma)
Title: Outflow Energetics in the Heart of NGC 1333: FIFI-LS Spectroscopy of the SVS13/HH 7-11 Region
Abstract: Protostellar outflows are one of the principle sources of feedback on molecular clouds during the star formation process, especially in regions where high-mass stars are not forming. The NGC 1333 cluster is one of the nearest low-mass embedded clusters and serves as a proto-type for embedded cluster studies. Furthermore, outflows from protostars in this region are important to maintaining turbulence, if not disrupting the natal cloud. The energy and momentum of the outflows are principally measured using low-J CO lines in the millimeter; however, the primary cooling lines are the high-J (J>10) CO lines in the far-infrared, which trace the energy injection into the molecular clouds. The most powerful protostellar outflows in NGC 1333 emanate from the small, central group of protostars that make up SVS13 (A, B, and C), but the far-infrared CO emission spectrum was never observed with Herschel. We propose FIFI-LS spectroscopy to observe four high-J CO lines (J=14-13, 17-16, 22-21, and 25-24) toward three positions: SVS13A, C, and the HH7 outflow shock. These lines will enable us to measure the CO rotation temperatures and the far-infrared CO luminosity in the region, thereby characterizing the shock conditions and total cooling from the CO lines, which is a large fraction of the cooling budget and reflects the amount of energy injection into the molecular cloud. This is important for regulating the star formation efficiency, which is crucial to characterize for this nearby, prototype embedded cluster.
Proposal ID: 06_0122
Principal Investigator: Gavin Rowell (University of Adelaide)
Title: C+ Mapping of the Brightest Gamma-Ray Supernova Remnant
Abstract: In this SOFIA propose we aim to use the THz-frequency fine structure line of ionised carbon, C+, to further trace the "dark" component of the ISM gas associated with the brightest-known TeV gamma-ray supernova remnant (SNR). Our target is the young SNR RXJ1713.7-3946 which still harbours the bulk of its sub-TeV cosmic-ray particles. The high cosmic-ray density inside the SNR bubble, about 4000 times higher than the Galactic average, could lead to significantly enhanced C+ abundance though ionisation of the neutral gas. We plan to map several parts of the SNR rim with the SOFIA upGREAT instrument that will allow us to look for variations in C+ across the SNR shock and regions with localised dense molecular and atomic gas. We will combine our map of C+ with new CO images at similar resolution to create the most detailed inventory of the total molecular column so far. Comparing this to the new TeV gamma-ray image from H.E.S.S., we can then finally start to quantify the level of cosmic-ray acceleration occuring in this prominent SNR, the brightest of its type in gamma-ray astronomy, and thus help to advance our understanding of where Galactic cosmic-rays come from. In addition, our study will provide new opportunities to follow the chemical production channels for C+, and its dynamics in a region under the influence of a very fast (>1000 km/s) and young (~1000 yr) SNR shock that has entered dense molecular and atomic gas regions.
Proposal ID: 06_0124
Principal Investigator: Philip Appleton (California Institute of Technology)
Title: Mapping extended [CII] emission in NGC 7319-A Seyfert Galaxy that may be driving Turbulence into the Stephan's Quintet Group Halo
Abstract: We propose to observe [CII] emission in NGC 7319, a nearby low-luminosity AGN, which has unusually powerful mid-IR-detected warm molecular hydrogen emission indicative of powerful shocks. Our proposal aims at exploring how H2, heated by shocks, can potentially boost the strength of [CII] emission at the jet-ISM interface. Following on from previous successful SOFIA observations of NGC 4258, we propose another similar galaxy, NGC 7319. This Seyfert galaxy in the Stephan's Quintet group, shows a collimated radio structure and bow shock at the base of a large-scale CO-emitting filament. Previous (incomplete) [CII] mapping of the Stephan's Quintet group by Herschel missed the region around NGC 7319, but showed tantalizing kinematic evidence, in the adjacent intergroup gas, for a possible influence from NGC 7319. The proposed observations will conclusively determine whether the AGN in NGC 7319 plays a role in creating turbulence on a large scale within the massive halo of the group by mapping the galaxy and tracing the jet's influence out into the previously mapped IGM. As more [CII] and [OI]-emitting galaxies and massive proto-galaxies are discovered at high-z, where turbulence is expected to be enhanced compared with nearby galaxies, it is important to study nearby spatially-resolved analogs. SOFIA provides the only current pathway to perform this work.
Principal Investigator: Timea Csengeri (Max Planck Institute for Radioastronomy)
Title: Do strong magnetic fields dictate the formation of the highest mass stars?
Abstract: Magnetic fields represent a critical ingredient to star formation, their exact role in controlling the mass assembly and the collapse process from clump to core scales is, however, extremely poorly constrained. Based on high angular resolution ALMA observations, we could identify the best targets where star formation is at its extremes: low luminosity early stage massive dense cores hosting up to 40Mo within 0.05pc scales, clearly hosting precursors to the most massive O-type stars forming in the Galaxy. Our pathfinder project aims to reveal the yet unexplored territory of magnetic fields on the 0.05 to 0.1 pc scales among these targets to answer the question whether strong magnetic fields are necessary to form the highest mass stars. The SOFIA/HAWC+ instrument provides a unique opportunity to tackle this question, its angular resolution matches that of the dense cores up to a few kpc, and its high sensitivity allows efficient and high sensitivity mapping to detect thermal dust polarisation. We will confront the derived field alignment and estimated field strengths to theoretical models of star formation.
Proposal ID: 06_0130
Principal Investigator: Silvia Leurini (INAF-Osservatorio astronomico di Cagliari)
Title: Far-IR cooling in massive YSOs
Abstract: Models (Tielens & Hollenbach 1985; Hollenbach & McKee 1989) and observations (e.g., Nisini et al. 2002; Karska et al. 2014) show that the cooling budget of low- and high-mass star forming regions is dominated by OI, CO and H_2O lines in the far-IR. However, our knowledge on the line far-IR cooling is based on observations with poor angular and spectral resolutions (ISO), and/or poor sensitivity (KAO). PACS on board Herschel allowed observations of OI, for example, with an improved angular resolution of 9".4, however without resolving the line profiles. In this proposal we aim to study the evolution of the main contributors of the far-IR line cooling with time during the formation of massive stars and to separate high-velocity outflows/jets from low-velocity emission or absorption. How does the contribution of each main species (OI, H_2O, CO) to the far-IR line cooling evolve with time? Which environment do they trace? Is the role of water as coolant negligible also at high-velocities in outflows? What is the contribution of warm atomic gas traced by OI on the overall jet/outflow system? These questions can be answered only with spectroscopically resolved observations of OI, CO and H_2O in a sample of massive sources in different evolutionary phases. Our team was awarded HIFI/Herschel and GREAT/SOFIA time to study water and high-J CO in the proposed sources. We now need GREAT observations of OI to obtain a complete view of the far-IR line cooling budget in the sample.
Proposal ID: 06_0131
Principal Investigator: Ranga-Ram Chary (Caltech/IPAC)
Title: Planck's Dusty GEMS: Measuring the AGN Contribution in the Brightest z~3 Star-Forming Galaxies in the Sky
Abstract: Hyperluminous (>1E13 Lsun) infrared galaxies detected at submillimeter wavelengths are among the most intense, star-forming galaxies in the Universe. Although they show signs of AGN activity in the X-rays and the mid-infrared, it is generally thought that their bolometric luminosity, most of which is emitted in the far-infrared, is dominated by star-formation and not by the AGN. Here, we propose to measure the AGN contribution in a population of high redshift (z~3) submillimeter galaxies detected through the Planck all sky survey which have been greatly amplified through gravitational lensing by a foreground galaxy. The SOFIA data bridge the gap in wavelength coverage that exists between the WISE 22 micron and Herschel 250 micron data - this is crucial for sampling the hot dust emission from a buried AGN and deriving robust bolometric luminosities. Our observations will also characterize the multiple components of thermal dust emission to critically assess the canonical view that high redshift starbursts appear to show a limited range of spectral energy distribution (SED) shapes in the far-infrared that is distinct from the SED of main-sequence star-forming galaxies. Since these SEDs have been the benchmark for characterizing the unlensed star-forming, submillimeter galaxy (SMG) population, the proposed observations will have an impact not just on our target sample but on the derived properties of the SMG population as a whole, such as their star-formation rate and gas/dust mass.
Proposal ID: 06_0142
Principal Investigator: Tom Megeath (University of Toledo)
Title: Bow-shocks and Jets in the Far-IR: Velocity Resolved Mapping of the OMC2/FIR Outflow with upGREAT
Abstract: The OMC2 FIR3 outflow is the closest intermediate mass protostar resolved in far-IR line emission by Herschel (distance 400 pc). Its 0.1 pc jet has the strongest [OI], high-J CO and H2O lines detected by the Herschel Orion Protostar Survey, making it an exceptional source for probing the origin of the far-IR emission in in outflows. Our GREAT [OI] and CO 16-15 spectra toward five position paint a surprisingly complex picture for the far-IR emission. To the north of the protostar, a high velocity component is present which may trace internal shocks within an outflow jet apparent in H2 emission. To the south of the protostar, where the outflow is interacting with dense gas, the CO and [OI] show line profiles are similar to those obtained in a CO 6-5 map of the outflow. The CO 6-5 position-velocity diagram shows that this transition traces the terminal shock of a jet-driven bow-shock and the shell of gas swept up by the bow-shock. This implies that the far-IR emission in the southern outflow is also dominated by the terminal shock and the shell of swept up gas. The unexpected dual nature for the far-IR emission - jets to the north and bow-shocks to the south - must be confirmed by mapping. We propose a large scale, 17" resolution map optimized for the LFA and a smaller, 6' resolution map optimized for the HFA to map the putative jet and bow-shock components, to confirm our interpretation, and to provide a comprehensive picture of the far-IR kinematics of this outflow. In particular, the lower shock velocities (~ 10 km s-1) implied by the swept-up shell challenge models of the high-J CO and [OI] emission, and thus confirmation of this picture is essential for understanding the full range of processes producing far-IR emission in outflows. Furthermore, by relating velocity components of the far-IR and CO 6-5 emission, we set the stage for proposing for ALMA 6-5 maps with the goal of resolving these components with arcsecond angular resolution.
Proposal ID: 06_0144
Principal Investigator: Edward J. Montiel (University of California – Davis)
Title: Determining How Mass--Lost Rates Impact the Chemical Abundances of Circumstellar Envelopes
Abstract: A relationship between the chemistry within the envelopes of AGB stars and the mass-loss rates has not been thoroughly investigated. Therefore, we are proposing high resolution spectral observations (R ~ 85,000) with EXES in order to examine the chemical abundances of the circumstellar envelopes of a sample of AGB stars with known different central star chemical abundances and mass-loss rates. We have selected two spectral regions in order to sample several molecules unavailable from the ground and/or with no permanent dipole moment: water and methane at 7.5 and carbon dioxide at 13.5 micron. Previous mid-IR spectrographs such as SWS on ISO or IRS on Spitzer lacked the necessary spectral resolution to perform these observations. These new EXES observations will allow us to identify many molecular lines in the observed spectral ranges. These features will be modeled with the aid of a radiation transfer code and will be used to build, in conjunction to complementary work at other wavelength, a coherent chemical model.
Proposal ID: 06_0145
Principal Investigator: Antoine Gusdorf (LERMA, ENS, Paris Observatory, Paris, France)
Title: The Far-infrared view of the Cepheus E protostellar outflow
Abstract: Protostellar jets and outflows play a critical role in the interstellar medium (ISM) of galaxies, in which they input energy in all possible forms: mechanical through shock waves they drive, far-UV photons from the protostar or from fast shocks, and cosmic rays that can be locally accelerated. They hence play an important role in the ISM evolution. We request to map the Cepheus E outflow from an intermediate-mass protostar in the [OI] 3P1-3P2 and [CII] 2P3/2-2P1/2 lines to better understand the physical processes associated to the outflow, as well as its energetic and chemical impacts. We will also probe the formation process of the young star and its outflow, and study the acceleration of particles in its energetic shocks. Combined with observations acquired by our team, these maps will be analysed in four steps. First, simple assumptions will be adopted (local thermodynamical equilibrium and large velocity gradient) to extract global first-order information (column densities, energetics). Then, the Paris-Durham model will be applied to better understand shock physics and chemistry in local knots. We will compare the outflows characteristics to models of outflows formation. Finally, a model of particle acceleration in protostellar environments will be used to assess the potential of this outflow to generate CRs. Our recent publications on this outflow have combined SOFIA, IRAM-30m, PdBI, JCMT, and Herschel observations. Cep E is not observable by ALMA, but we have acquired PdBI data to perform astrochemical studies. We will propose to observe the outflow with JWST, in particular in H2 lines that provide excellent diagnoses to the physical conditions in shocks. A map of the entire outflow in [OI] at 6'' resolution would be an unprecedented showcase of SOFIA's capabilities. At least one article will be dedicated to these observations. Our further studies will make use of this rich dataset.
Principal Investigator: Stefanie Walch (I. Physics Institute)
Title: [CII] line emission as an indicator for dynamical molecular cloud formation in Taurus}
Abstract: The [CII] fine structure transition line at 1900.5369 GHz traces CO-dark molecular gas in and around molecular clouds. Theoretical models predict that [CII] should be detectable around quiescent, newly forming molecular clouds. We aim to find [CII] line emission near a relatively sharp ridge at the lower edge of the L1536 region in the Taurus molecular cloud with upGREAT onboard SOFIA. The L1536 ridge is likely caused by the dynamics of molecular cloud formation. It is therefore the ideal location to study [CII] as a tracer for CO-dark molecular gas in a relatively isolated region of a young molecular cloud, which is presently in formation. We will compare the observed line profile and integrated intensity with 3D MHD simulations of molecular cloud formation, which feature a chemical network and are used to predict the emissivity in [CII] of the forming molecular cloud by means of synthetic observations. In the synthetic emission maps, we locate several regions which resemble the edge of L1536 and predict an integrated intensity of ~100 mK km/s which is observable with SOFIA upGREAT. The comparison allows us to verify (or to falsify in case of a non-detection) the predictive power and applicability of MHD simulations using chemical networks. We ask for 3.78 hours of total observing time to complete the proposed task.
Principal Investigator: Maitraiyee Tiwari (Max Planck Institute for Radio Astronomy)
Title: Unveiling the remarkable Photodissociation region of M8
The Lagoon Nebula, M8, is the most prominent star-forming region in the section of the Sagittarius-Carina Arm lying near our line of sight towards the Galactic centre. The brightest star of M8, Herschel 36, is responsible for ionising HII region of NGC 6523 and the Hourglass Nebula. With the discovery of second strongest galactic CO line emission towards Herschel 36, M8 is one of the brightest Photodissociation Regions (PDRs) in our Galaxy. It is surprising that it has been largely unexplored in the millimeter-and submillimeter regime. We are studying the effects of far-UV photons on gas in the vicinity of a bright star with the aim of establishing M8 as a new template for luminous PDRs. The major cooling lines of a PDR are the fine structure lines [CII] and [OI] observable in the far-IR. Where [CII] 157µm probes the low density parts of a PDR, [OI] 63µm line probes the high density parts. [CII] along with high-J CO transitions were successfully observed in May 2016 and the results obtained from them are soon to be published (Tiwari et al., 2017 in prep.). The densities and FUV field flux calculated for M8 are high suggesting [OI] lines to dominate the cooling process in M8. Observations of these lines are therefore crucial to complete our study of M8. Hence, we intend to observe [OI] 145 Âµm and 63µm emission lines towards Herschel 36 using SOFIA's upGREAT receiver bands.
Proposal ID: 06_0148
Principal Investigator: Pedro Salas (Leiden Observatory)
Title: Mapping 158 micron [CII] emission from the envelope of a molecular cloud
Abstract: In this program we propose to map the 158 micron [CII] line towards the south-west of the supernova remnant Cassiopeia A. Detailed analysis of the interstellar medium structure in front of Cassiopeia A has revealed that here it is possible to study the interface between predominantly atomic and molecular gas in the outer Galaxy. By measuring the 158 micron [CII] line in this region we aim to determine the gas cooling rate and its energy budget. This will be compared with the gas physical conditions to determine how the cooling rate changes as a function of the gas pressure and environment. Additionally, the spatial and velocity structure of the 158 micron [CII] line will be compared with that of other tracers of the cold interstellar medium such as millimeter wavelength CO, 18 cm OH, 21 cm HI and low frequency (<1 GHz) carbon and hydrogen radio recombination lines. With this we will determine how much of the observed 158 micron [CII] emission comes from the atomic, molecular and ionized phases of the interstellar medium. SOFIA and the upGREAT instrument make it possible to map the 158 micron [CII] line spatially and velocity resolved in under 2.5 hours in the 280''x140'' region we aim to map.
Proposal ID: 06_0150
Principal Investigator: Jonathan Tan (University of Florida)
Title: The Inception of Star Cluster Formation: [CII] emission from IRDCs - II. Massive Protoclusters and Testing GMC Collision Models for Triggered Star Formation
Abstract: Most stars are born in clusters. Thus, the processes that may initiate star cluster formation are of fundamental importance throughout astrophysics, from the evolution of stellar populations in galaxies to the formation of planets in protoplanetary disks in these environments. Infrared Dark Clouds (IRDCs) are now recognized as the likely precursors of star clusters. Thus it is important to understand the kinematics, dynamics & formation environments of IRDCs. We propose to utilize the efficient OTF mapping capabilities of upGREAT to map [CII] and [OI] emission in a sample of 4 IRDCs that we have been studying over the last decade with numerous facilities, including Spitzer, IRAM 30m, IRAM PdBI, Herschel Chandra & ALMA. [CII] probes the photodissociation region around the IRDC. Thus it provides crucial information on the kinematics of the gas that is becoming molecular and joining the IRDC. Different theoretical models of IRDC formation are expected to have different signatures of [CII] kinematics. For example, simulations of dense gas formation via either decaying turbulence or triggering by cloud-cloud collisions make specific distinguishing predictions for [CII] spatial and kinematic structures. These will be tested against upGREAT observations to deduce the processes that initiate star cluster formation. This proposal follows on from our Cycle 4 project, which started mapping one of the IRDCs in the sample.
Principal Investigator: Carsten König (MPIfR Bonn)
Title: [CII] in the Low-Metallicity Environment of the Outer Galaxy
Abstract: To investigate the influence of decreasing gas metallicity on star formation with respect to Galactocentric distance R_gal, we propose to make [CII] observations towards newly revealed molecular clouds in the outer Galaxy, carefully selected from the analysis of Herschel far-infrared data together with APEX CO and [CI] follow-up observations. These observations will not only allow us to study the ionized carbon content of star forming clumps at large R_gal relative to the already measured molecular bound carbon in CO and atomic carbon, but also let us investigate the "CO-dark" H_2 gas fraction wich is found to increase with increasing Galactocentric distance R_gal (Pineda et al. 2013), but was never before investigated for R_gal>11kpc towards the outer Galaxy. These measurements of [CII] together with the Herschel continuum emission data, APEX CO isotopologues and atomic carbon data will be used to investigate the influence of environmental parameters that are known to change with Galactocentric distance (such as e.g. metallicity, density, UV- radiation field, etc.) on the properties (such as temperature, virial- and cloud-mass, luminosity, gas-to-dust ratio) and molecular abunance ratios of molecular clouds in the outer Galaxy.
Principal Investigator: Juan Diego Soler (Max Planck Institute for Astronomy)
Title: The magnetic field structure in the Musca filament at 0.01 pc scale
Abstract: Filamentary structures play a central role in the evolution of molecular clouds, however, their dynamical properties remain poorly characterized. A long-standing problem in the understanding of filamentary structures is what is the role of magnetic fields in their stability. One key diagnostic for addressing this problem is the morphology of the magnetic field in filaments. Specifically, the helical morphology has been suggested as one important possibility, but observational evidence of such a field configuration is scarce. We propose to evaluate radial profiles of the polarization orientation, polarized flux, and polarization fraction across a filament to test whether or not magnetic fields have a helical morphology. This enables us to address the fundamental hypothesis that helical magnetic fields support filaments against gravitational collapse. We have identified an outstanding target, the Musca filament (d=160 pc), to apply this analysis. Here, we propose to use the HAWC+ instrument to observe polarized dust emission at 217 microns towards Musca. We will use the data to evaluate the presence of helical magnetic fields and their relation to the column density and velocity field of the filament. Regardless of whether or not we identify helical fields, our observations will constrain the field morphology at spatial scales below those sampled by Planck, that is, less than 0.2 pc, and evaluate their role in the evolution of filaments.
Principal Investigator: Nicola Schneider (I. Physik. Institut; University of Cologne)
Title: CII emission in high-latitude clouds
Abstract: After our first detection of the [CII] 158 micron line in the diffuse high latitude cloud Draco, we propose to extend our study of this class of clouds and observe two points in [CII] in the Spider region. The physical properties (column density, temperature, radiation field) of this cloud are comparable to Draco, but the complex HI velocity structure (e.g. strong shears) of Spider suggests strong density variations leading to the dynamical formation of molecular gas. The [CII] line traces the HI-H2 transition, and is probably the most important cooling line for the CNM (cold neutral medium with T around 100 K). We expect weak [CII] emission but maybe with large line widths if shocks (possibly causing the strong HI velocity shears) are involved. The observations will be compared to predictions of cloud formation models that include chemistry, and photon dominated region models. The [CII] observations will ultimately help us to better understand the gas composition of diffuse clouds, in particular the properties of high-, intermediate-, and low-velocity clouds (HVCs, IVCs, and LVCs), their formation, and evolution.
Proposal ID: 06_0154
Principal Investigator: Ralf Siebenmorgen (ESO)
Title: Origin of the IR excess of massive stars
Abstract: We have obtained a sample of OB stars, including several main sequence stars, and find that more than half of these massive stars (13/23) show prominent IR excess in Spitzer/IRS. The IRS spectra can be explained assuming two distinct scenarios, either IR free-free flux, as derived from radio upper limits and wind models with a far IR fluxes following a λ^-0.6 law, or circumstellar/debris dust with its typical spectral energy distribution and as known for low mass counterparts such as beta Pic. Far IR/submm photometry between 80-220µm is needed to confront the potential dust emission against a λ^-0.6 free-free wind component. Today this observing range is only accessible by SOFIA equipped with HAWC. We propose observing three of our massive stars that are selected to display the strongest and brightest IR excess in HAWC filters band C (89µm) and band E (214µm). The total observing time request is 4.4h. Such observations will allow an unambiguous conclusion on the origin of the IR excess of massive stars. The discovery of dust debris around massive stars will link the high- and low-mass star-forming regimes, and opens a new window for the potential detection of planets around massive stars. Interpreting the data with our radiative transfer models will constrain the dust size distribution and mass. Our findings will have consequences for the dust survival process and may open a new dust reservoir in starbursts at high redshift (z > 6). (This is a re-submission of our previously approved HAWC proposal adjusted to the new sensitivity.)
Principal Investigator: Rolf Gusten (MPIfR)
Title: Dense Neutral Gas in the Galaxy's Central Molecular Zone: The Sgr C Region
Abstract: We aim to add to our understanding of the Galactic center and galactic nuclei in general by searching for CO-dark dense neutral gas associated with the SgrC complex. upGREAT's dual focal plane arrays provide an order of magnitude improvement over Herschel-HIFI for the [C II] line and allow velocity-resolved observations of the [O I] line for the first time. Gas in and near Sgr C may be streaming into the center from crossing x_1-x_2 orbits or associated with swept-up material from supernovae or colliding clouds. Comparison of [C II], [O I], and complementary molecular observations with APEX will firmly establish the location and kinematics of all dense neutral gas components in the region. This is also the second sub-project within a long-term project to produce velocity-resolved [C II] and [O I] data cubes for the Galaxy's entire Central Molecular Zone (CMZ) with uniform sensitivity, velocity resolution, and sampling.
Proposal ID: 06_0160
Principal Investigator: Michael Person (MIT)
Title: Monitoring Titan's Atmosphere in the Post-Cassini Era with Stellar Occultations
Abstract: With the coming end of the Cassini/Huygens mission (the Cassini Grand Finale is expected to end with the termination of the spacecraft in September 2017), our monitoring of Titan’s atmosphere will once more depend solely on Earth-based observations. Stellar occultation measurements made from Earth, most recently in 2003, differ from the atmospheric profile measurements made in the upper atmosphere during the 2005 Huygens Atmospheric Structure Instrument (HASI) descent phase, although they agree in the lower atmosphere. Reconciling HASI data with Earth-based occultation data provides a constraint on haze constituents and production in Titan’s atmosphere, but only if all other conditions are assumed to be constant. It is an open question if Titan’s atmosphere undergoes significant seasonal variation as Titan’s atmospheric profile has not been looked at from the ground since the 2003 event (14 years ago) and so occultation/HASI discrepancies may still be attributed either fully to particle extinction, variability in the atmospheric profile, or more likely, some combination of the two. Without further occultation data, the Cassini/HASI descent profile will continue to lack the context to fully evaluate its results, and time variability of Titan’s atmosphere can only be detected and understood through continued measurement. SOFIA's unique ability to be reliably placed in the central flash region of occultation events where the richest dataset is available, and its immunity to low-level weather disturbances make it the ideal platform for beginning to answer these outstanding questions on this important body. We therefore propose to use SOFIA with the FPI+ to measure the radial profile of Titan’s atmosphere by observing two stellar occultations by Titan (in concert with supporting ground observations) which will be visible over the United States during June of 2018 and over Australia/New Zealand in July of 2018 during the expected Southern Deployment.
Proposal ID: 06_0162
Principal Investigator: Joseph Hora (Harvard-Smithsonian Center for Astrophysics)
Title: Spectroscopy of Massive Protostars in Cygnus-X
Abstract: High mass star formation is much more poorly understood than low mass star formation; this is in part due to the greater distance, extinction and confusion toward regions of high mass star formation and due in part to the rapid evolution of high mass protostars and difficulty of finding such objects in the earliest stages of their evolution. Cygnus-X is unique target for such a study, being relatively nearby and containing a large number of protostars at a common distance. Obtaining observations of large unbiased samples of massive protostars covering a range of evolutionary stages is an important step toward understanding their evolution. We propose to use FORCAST on SOFIA to obtain 5-40 micron spectra of a sample of massive stars that are forming in the Cygnus-X region. The sample will complement our existing Spitzer/IRS data by enabling us to span a range of mass and evolutionary stages in Cygnus-X, allowing us to probe with some of the best statistics available the earliest stages of massive protostars. These objects are too bright for JWST, but are the Galactic equivalent of objects that JWST will study in more distant Galactic regions and in other galaxies. The SOFIA results will enable us characterize the high end of the mass distribution in Cygnus-X. We will also be able to examine the effect that these stars have on their surroundings through outflows and radiation.
Proposal ID: 06_0163
Principal Investigator: Angela Cotera (SETI Institute)
Title: Star Formation in the Galactic Center: FORCAST observations of Sgr B1
Abstract: The proximity of the center of our Galaxy enables us to study star formation under conditions commonly found in other galaxies, but at spatial resolutions unachievable elsewhere. The GC provides unparalleled opportunities to test theories of the interrelationship of massive stars, warm and hot gas and dust, turbulent giant molecular clouds, large-scale magnetic fields, and a black hole. The region known as Sagittarius B is one of the most complex star-forming regions in the galaxy, containing a massive molecular cloud, dozens of HII regions, and numerous young stellar objects (YSOs). It is composed of two distinct regions Sgr B1 and Sgr B2. Although much of Sgr B is unobservable at IR wavelengths due to extinction, Sgr B1 has lower extinction. We propose to obtain FORCAST observations at 25.4 and 37.1 microns to complete observations first undertaken in Cycle 3. We will use these observations, in conjunction with the already executed FORCAST and FIFI-LS observations, and upcoming FLITECAM and FIFI-LS observations, to create a comprehensive picture of the stellar population, gas density and temperatures, and dust properties in Sgr B1. When further combined with existing multi-wavelength surveys of this region, we will be able to comprehensively address crucial questions such as: Is star formation in Galactic nuclei fundamentally different due to the extreme conditions found within these regions? How does the stellar feedback from massive star formation impact turbulence in giant molecular clouds? Does Sgr B1 fit in the proposed model of sequential star formation as streams of molecular gas pass by the super massive black hole Sgr A*?
Principal Investigator: Jürgen Kerp (University Cologne)
Title: Feeding the Milky Way Galaxy by cold gas accretion?
Abstract: We propose to study the [CII] emission line towards two intermediate velocity clouds (IVCs) located within the disk-halo interface. Both IVCs appear as twins in HI 21-cm line emission but differ significantly in their far-infrared emission. Most probably both IVCs are in a transient phase from atomic to molecular clouds but at different evolutionary stages. Here, we propose to explore the luminosity of the [CII] line in this transformation process. We expect that the dominantly atomic IVC is bright in [CII] while the already molecular IVCs shows up with typical brightness temperatures for IVCs. The proposed SOFIA upGREAT observations are crucial for our understanding of the fueling of the Milky Way's star formation with sub-solar metallicity gas.
Proposal ID: 06_0165
Principal Investigator: Tracy Huard (University of Maryland)
Title: Resolving Protostars in the Dense Core L1251A: A Look into a Small Young Group
Abstract: The Spitzer Space Telescope and Herschel Space Observatory have surveyed nearby star-forming regions, resulting in an enormous census of protostars and young stellar objects in a wide variety of environments, from those forming a single star to those forming large clusters. Much of the detailed modeling of core collapse and the formation process has focused on the former, while most stars form in clusters. A natural next step is to focus on modeling of small groups, such as L1251A. With four blended sources likely forming in a common envelope, L1251A is an ideal target for SOFIA/FORCAST as all of these sources may be observed in a single field of view and deblended, enabling this small group to be characterized and "primordial" conditions of this young group traced. Reliable spectral energy distributions will be constructed, yielding luminosities and robust source classifications to compare their evolutionary stages. These observations may inform and constrain radiative transfer models extended to handle such small, young groups.
Proposal ID: 06_0167
Principal Investigator: Alycia Weinberger (Carnegie Institution of Washington)
Title: Monitoring Dust Variability in an Extremely Dusty Disk
Abstract: The extreme debris disk of BD+20 307 was probably generated in a giant collision between planetary-scale bodies, perhaps akin to giant impacts that shaped the early solar system. This old star hosts a warm ring of dust at about 0.85 AU that is orders of magnitude more dusty than any other star its age. Because of its extreme dustiness and the location of its debris so close to the star, the timescales for changes can be years rather than millennia. Stochastic release of small particles and collisions of planetesimals of various compositions over time may change the location, size distribution, and composition of the resulting dust. All of these imprint a signature on the 8-24 micron spectrum. We therefore propose to re-observe BD+20 307 with FORCAST to complete its spectrum with SOFIA, having already obtained 8-13 micron data from our first approved observing program. With the complete dataset, we will compare its spectrum now to those taken with Spitzer over three collisional lifetimes ago. BD+20 307 is a rare place where we can actually search for evolution resulting from an extreme impact manifested in changes in the composition of the debris with time. Our understanding of collisional cascades comes from aggregate samples of stars at a range of ages. This is an opportunity to test cascade models against a system evolving in real time.
Proposal ID: 06_0170
Principal Investigator: Alexander Tielens (Leiden Observatory)
Title: 30 Dor [CII] survey
Abstract: We propose to map the [CII] 158µm emission associated with the 30 Dor super star cluster in the LMC over a region of about 25x25'. This data will be combined with existing, Chandra and XMM studies of the hot gas, HST optical studies of the ionized gas, Spitzer studies of the PAHs and Herschel studies of the UV-heated dust grains in the neutral photodissociation region, and ALMA studies of the molecular gas. In this way, we can trace the feedback of massive stars on their environment. Specifically, the [CII] survey will allow us to determine the kinematics of the shells of neutral gas swept up by the large, hot gas filled bubbles created by the stellar winds and supernovae in this region. The kinetics of these shells can then be compared to the thermal energy of the hot gas to determine the overall energetics of the region and assess the role of hot gas (as opposed to radiation pressure) in the expansion of the region. In addition, the [CII] 158µm line dominates the cooling budget of the neutral gas in the photodissociation region and we can use the planned observations to trace the radiative interaction of the massive stars with the surrounding gas. Finally, the planned observations will provide insight in the use of the [CII] line as a tracer of star formation in the early universe; in particular, whether such [CII] emission traces the extreme environments of star burst or more benign regions of massive star formation such as Orion.
Principal Investigator: Michael Rugel (MPIA Heidelberg)
Title: [CII] and OH gas in different galactic environments
Abstract: CO-dark gas amounts to a significant fraction of galactic molecular gas. The OH molecule is suited to trace this gas component. It is an early molecule to be formed in the oxygen chemistry and may be present in diffuse atomic and molecular gas. Investigation of the correspondence of OH absorption with emission from diffuse atomic and molecular regions is indispensable to locate the ISM phase of the OH gas. [CII] may be one of the best tracers of transition regions between atomic and molecular gas. We therefore aim to compare existing OH absorption measurement from The HI, OH, Recombination Line survey of the Milky Way (THOR) data to [C II] emission. The OH absorption measurements have been analyzed, they have been compared to publically available 13CO emission data as molecular gas tracer and will be presented in a forthcoming paper. We were also awarded time for follow-up observations of OH ground state transitions at higher spectral resolution and superb sensitivity, which have been partly observed already. Here, we propose to observe the [C II] 158 micron transition with the upGREAT instrument on SOFIA, to compare the kinematics and abundances to those of OH. This will be done for a subsample of THOR sources, which include representatives from CO-bright detections, which are associated with HII regions, to CO-bright detections without HII region association to CO-faint and CO-dark lines of light. While our focus is on [CII] observations, the upGREAT receiver allows for simultaneous observation of the [OI] 63 micron line, which will provide constraints of the oxygen gas phase abundance in different ISM phases.
Proposal ID: 06_0172
Principal Investigator: José Pablo Fonfría (Instituto de Ciencia de Materiales de Madrid)
Title: The pure rotational spectrum of H2 toward the AGB star IRC+10216
Abstract: The Asymptotic Giant Branch stars (AGBs) are evolved stars surrounded by a circumstellar envelope (CSE) composed of molecular gas and dust. The most abundant molecular species in these CSEs is H2 by far. However, this molecule has never been observed towards this kind of stars due to the lack of permanent dipole moment which forbids the electric dipole transitions in the electronic ground state and to the non-existent UV radiation field emitted by the central star that could electronically excite the H2 molecules. Because of these facts, the part of its spectrum that we could use to observe H2 is extremely weak and a huge column density is required to produce observable lines. This is the main reason for what other molecules such as CO are commonly used to derive structural information of molecular environments although H2 would be the best suited to do this task if its spectrum would be stronger. In any case, H2 has been unsuccessfully searched for a long time in AGB stars mainly because of the high atmospheric opacity from ground. However, we recently performed high spectral resolution observations in the range 5.6-7.2µm toward the very bright AGB star IRC+10216 with the EXES spectrograph mounted on SOFIA. In this spectral survey we found a weak feature at the frequency of the rotational H2 S(5) line that seems to be formed in the innermost CSE, the region of the envelope where one would expect the actual H2 line to be formed. New observations of other H2 lines are needed to confirm this detection. Hence, we propose to observe IRC+10216 at the frequencies of the o-H2 lines S(1), S(5), and S(7) with the EXES spectrograph from SOFIA, taking advantage of the very low atmospheric opacity existing at an altitude of 40,000 ft.
Proposal ID: 06_0173
Principal Investigator: Andrew Harris (University of Maryland)
Title: Dense Neutral Gas in the Galaxy's Central Molecular Zone: Gas Flows in Sgr A
Abstract: The black hole at the center of our galaxy is mysteriously quiescent at the moment, but X-ray echoes show signs of occasional or episodic bursts of activity on timescales of a few hundred years. Our observations are geared to understanding the possible sources of accretion activity. We aim to add to our understanding of the Galactic center and galactic nuclei in general by searching for CO-dark dense neutral gas that may be streaming from the large molecular clouds near the center to the Circum-Nuclear Disk (CND), or in other directions across the very center. Observations of [C II] and [O I] will trace dense neutral gas components that are missing in molecular line tracers. Combining these far-IR lines with complementary molecular observations from APEX will firmly establish the location and kinematics of the dense neutral gas over large scales close to the center. This is also a sub-project within a long-term project to produce a high-quality [C II] and [O I] data cube for the entire Central Molecular Zone (CMZ) with uniform sensitivity, velocity resolution, and sampling.
Proposal ID: 06_0175
Principal Investigator: Noel Richardson (University of Toledo)
Title: Modeling the dust formation and detecting PAHs around carbon-rich Wolf-Rayet binaries
Abstract: A recent reanalysis of ISO spectroscopy of dust-forming Wolf-Rayet binaries shows that these systems produce PAHs in their environments. It is thought that these PAHs may be the precursors of amorphous carbon dust, and that the systems are important to the overall Galactic dust budget. We propose to obtain new, high signal-to-noise SOFIA/FORCAST grism spectroscopy of several WC stars, examining the diversity of the environments that form such dust and molecules, while also looking for long-term changes in the dust production with comparisons to archival ISO spectroscopy. Further, these new data will allow us to model the dust composition in the system, gaining new insights into the dust creation rate for WC stars, and their relative importance in the Galactic dust budget. Further, we will compare these results to that of models made for the wind emission in the optical and near-infrared, yielding precise measurements of gas-to-dust ratios in these harsh environments.
Proposal ID: 06_0177
Principal Investigator: Sylvain Bontemps (Laboratoire d'astrophysique, University of Bordeaux)
Title: [OI] 63 micron emission as a tracer for low-velocity shocks
Abstract: Stars are believed to predominantly form in filaments which may originate and evolve as (low velocity) shock confined dense structures. The expected C-shocks should cool by FIR-line cooling with a possible important contribution from the OI 63micron line. We propose to make an attempt to detect for the first time OI emission from such a low velocity shock at the surface of the young, and simple filament Musca. Cooling from oxygen in the ISM is generally a very important issue for ISM equilibrium and in the context of energy (turbulent) dissipation. Such a first SOFIA detection of the [O I] line, unambiguously associated with turbulent motions would clearly confirm the dynamical scenario to form filaments and would point to a large amount of atomic oxygen in the ISM, crucially implying an important effect of atomic oxygen on the global cooling in dense molecular clouds.
Principal Investigator: Paola Caselli (Max-Planck-Insitut für Extraterrestrische Physik)
Title: OD and the origin of water in protostellar cores
Abstract: We propose to observe with SOFIA the ground-state rotational lines of OD at 1.39 THz ( 216 micron) and of OH at 2.514 THz (119 micron) towards low-mass and intermediate-mass protostars with massive, cool envelopes. The lines are predicted to be detected in absorption against the strong far-infrared continuum from the central source. The OD data will be combined with HDO observations, with the goal of disentangling grain-surface and gas-phase production pathways of OH and H2O, which form in similar reactions as OD and HDO. Water and the hydroxyl radical are at the heart of the oxygen chemistry, and important for the production of complex organic molecules. Our chemistry model predicts that the OD/HDO abundance ratio obtains much smaller values on grain-surfaces than in the gas-phase. Therefore, the OD/HDO and OD/OH ratios can be used to infer the origin of OH and H2O detected in protostellar envelopes, i.e. whether they are primarily produced by gas-phase chemistry or by desorption from the icy mantles of grains.
Proposal ID: 06_0180
Principal Investigator: Thushara Pillai (Boston University)
Title: Magnetic Fields in Massive Filaments
Abstract: Magnetic fields pervade galaxies, shaping them from the largest scales to the smallest star forming scales. A firm understanding of their role is crucial to our understanding of the physics of ISM. A dominant phase of the ISM that has received considerable attention is that of filaments which are ubiquitous and dominate the mass reservoir in molecular clouds. Enormous progress has been made recently towards understanding filament properties. The next major step should be to understand the role of magnetic fields in filaments. We propose to take advantage of HAWC+ dust emission polarimeter now available on SOFIA to launch a pilot polarization study towards three major classes of filaments: (i) Pristine (ii) Hub-Filament systems and (iii) Perturbed. HAWC+ will trace the connection between the star forming cores and the filaments enveloping them. By covering a vast range in parameter space from quiescent to active filaments, we will be constraining the initial conditions prior to star formation, during star formation and after star formation (feedback from newly formed stars on their parent clouds.) The interpretation of observations will be supported by extensive custom--made numerical simulations of magnetized clouds and subsequent dust radiative transfer with various grain alignment mechanisms, as provided by collaborators. Combined, these observations will provide the first panoramic view of the magnetized nature of massive filaments in the ISM.
Principal Investigator: Bringfried Stecklum (Thuringer Landessternwarte - Karl-Schwarzschild-Observatorium)
Title: Monitoring the SED variability caused by the accretion burst from S255IR-NIRS3
Abstract: In spring 2016 our first epoch FORCAST/FIFI-LS observations of the outbursting high-mass young stellar object (HMYSO) S255IR-NIRS3 revealed a dramatic change of its spectral energy distribution (SED) due to the heating of its circumstellar disk by the burst. Our second epoch FIFI-LS data taken one year later show a decline of the FIR fluxes which indicates that the disk is cooling already, contrary to our expectations. Since the SED variability reflects the thermal changes in the disk, the analysis of this variability using time-dependent radiative transfer modeling allows us to derive major disk properties and to study their temporal behaviour. This will be shedding light on the formation mechanism of massive stars as well as delivering new insights on the physics of their circumstellar disks. Since SOFIA is the only facility to trace the temporal evolution of the SED at MIR/FIR wavelengths, we ask for continuation of our monitoring by performing third epoch measurements using the same instruments to extend the time coverage of the NIRS3 SED data base.
Proposal ID: 06_0183
Principal Investigator: Fabio P. Santos (Northwestern University)
Title: A tomography of the magnetic field structure in IRDC G14.2: massive filaments from large to small scales
Abstract: The process that regulates the formation of massive stars is complex and poorly understood. Such stars are formed deep within dense dusty filaments which fragment, leading to molecular cloud clumps, dense cores, and finally protostars. Theoretical work indicates that magnetic fields play a crucial role in the fragmentation process, but this has never been verified observationally. IRDC G14.2 is one of the best studied massive filamentary systems in the Milky Way, and an ideal laboratory to test theoretical fragmentation studies. The goal of this project is to directly test filament fragmentation theories and combine polarization measurements of IRDC G14.2 from different observatories (SOFIA, SMA, CSO, OPD-LNA) to provide a complete view of the magnetic field structure covering about three orders of magnitude in size scales (from several tens of parsecs to approximately 0.01 pc). Our in-depth study of the magnetic field structure is unparalleled for massive filaments: the widely different wavelengths used by each observatory will effectively allow a tomography of the magnetic field lines, unveiling how it varies along different layers as we go from the cloud's outskirts to its dense cores. SOFIA/HAWC+ observations will provide the fundamental missing connection between the large scales (probed by optical and near-infrared data, OPD-LNA) and the very small scales (probed by upcoming highly ranked SMA polarimetric observations). Previous SMA observations showed a different level of fragmentation between two of the most massive filaments in IRDC G14.2, suggesting different magnetic field strengths. We will calculate the field strength, providing a novel and direct test for theoretical work on massive filament fragmentation. In addition, we will evaluate the energy balance between gravity, magnetic fields and turbulence on different angular scales to identify the dominant energy component for different cloud depths.
Proposal ID: 06_0184
Principal Investigator: Sarah Sadavoy (Smithsonian Institution Astrophysical Observatory )
Title: Testing the Response of Dust Grains to Magnetic Fields in Perseus B1
Abstract: Magnetic fields in our Galaxy are often traced by polarized emission from dust grains. Nevertheless, dust grains are not homogeneous, and different dust grain properties can change the observed polarization. To test how measurements of the magnetic field are affected by dust properties, we will observe the B1 clump in the Perseus molecular cloud in dust polarization with HAWC+ in Band E (214 µm). The B1 clump shows evidence of dust grain growth toward its dense cores, providing the means to compare how both density (scale) and grain size affect polarization. We will also characterize the magnetic field structure across the diffuse cloud material over ~300 independent beams. From these observations, we will determine how different dust grain properties affect the observed polarization. This proposal represents a pilot study with B1 and will be expanded to compare dust polarization and dust grain properties in other star-forming regions.
Proposal ID: 06_0189
Principal Investigator: Quang Nguyen-Luong (Korean Astronomy and Space Science Institute)
Title: Probing the effects of shocks and radiation field in Young Embedded Massive Protocluster with [CII] and [OI]
Abstract: To understand the role of shocks and radiation field in star and molecular cloud formation and destruction, we propose to observe simultaneously the CII 158micron and the OI 63 micron line in the W43-Main regiom, a well-studied young embedded massive protocluster with a complex but clearly defined geometry and strong ionizing flux. We will use \CII\ and \OI\ to trace emission from PDsR and shocks and couple with dedicated models to determine their sensitivities with the environment. Combining with SiO observation that revealed ubiquitous low-velocity shock is in W43-Main filament/ridge network, \CII\ is essential to probe the silicon chemistry. In addition, we will also compare the atomic gas (CII and OI) with other spectrally resolved tracers such as CO tracing molecular gas, HCO+/HCN tracing dense gas, mm-recombination lines for the hot ionized gas, C2H2, C3H2 tracing PDR, that we already obtained with other observatories. SOFIA is the only instrument that provides spectrally and spatially resolved data of CII and OI that are required to complement our large data set we have acquired over the years with the IRAM 30m, PdBI, ALMA, and Herschel.
Proposal ID: 06_0191
Principal Investigator: Christy Tremonti (University of Wisconsin-Madison)
Title: Probing Dust-Obscured Star Formation and AGN Activity in Massive Ultra-Compact Galaxies
Abstract: We have discovered a rare population of extremely compact massive galaxies at z~0.5 that have extraordinarily high star formation surface densities. The galaxies are in the final stages of highly dissipational mergers and they host powerful ionized and molecular gas outflows. Based on the existing optical and mid-infrared data, we hypothesize that the outflows are powered by star formation, but constraints on the far infrared spectral energy distributions (SEDs) are needed to conclusively rule out contributions from obscured AGNs. We propose to use HAWC+ in total intensity mode with the C and E filters to measure the SEDs of two galaxies from 60-140 µm in the restframe (90-215 µm observed). We will combine this data with our existing 0.1-14 µm observations to measure the bolometric output of these systems, decompose their SF and AGN activity, and test whether the winds can be driven by star formation. The galaxies are excellent lower redshift analogs of the z > 3 progenitors of today's massive early-type galaxies and they provide us with an unprecedented opportunity to study star formation and feedback at its most extreme. Notably, no objects of this nature have existing measurements in the far-IR, so HAWC+ will enable entirely new science.
Proposal ID: 06_0193
Principal Investigator: Ilse De Looze (University College London)
Title: Dust polarisation properties in the Crab Nebula
Abstract: The large reservoirs of dust observed in some high redshift galaxies are difficult to explain without core-collapse supernovae (CCSNe) as a dominant dust production source. Theoretical studies tend to support efficient dust condensation in CCSNe, but the number of CCSNe with robust detections of >0.1 Msun of dust remains scarce (SN1987A, Cas A, Crab Nebula). Our lack of knowledge on the composition of freshly produced grains make supernova dust masses uncertain by factors of a few. The average size of supernova dust will furthermore strongly affect the fraction of grains that will survive supernova shocks before mixing with pre-existing interstellar dust. Larger grains would be less susceptible to shock processing, but the absence of constraints on the average supernova grain size make it impossible to anticipate the net dust production efficiency of CCSNe. Dust polarisation levels sensitively depend on the size, shape and composition of dust grains, and provide a unique way of constraining the nature of supernova dust species. We propose SOFIA HAWC+ polarimetric observations of the Crab Nebula at 89 and 154 micron targeting the peak of the dust SED emission. The Crab Nebula is an obvious target for dust polarisation studies with the recent detection of a large dust reservoir (0.2-0.5 Msun) and the absence of any surrounding ISM material that could contaminate dust polarimetric observations. The characterisation of grain composition will allow us to quantify the exact mass of freshly condensed grains in the Crab Nebula and will provide invaluable constraints on the carbon yields for nucleosynthesis models of progenitors with initial masses of 9-10 Msun. The inferred grain size will be crucial to determine the resistance of supernova dust to shocks and to infer the net supernova dust mass that is eventually injected into the ISM, which is vital to understand whether CCSNe are able to account for the large dust masses detected in high-redshift galaxies.
Proposal ID: 06_0198
Principal Investigator: Hector Arce (Yale University)
Title: The impact of winds from young intermediate-mass stars on their surroundings
Abstract: Recent studies have shown that young (pre-main sequence) intermediate-mass stars drive spherical winds that could be as important as outflows or HII regions as a source of stellar feedback in clouds. However, very little is known about these winds and their impact on their surrounding environment, as they have only been studied using molecular line (CO) maps. The mid-mass stars that power these winds drive PDRs (but are not massive enough to drive HII regions), and therefore the existing CO data of these sources provide a very limited view of the influence of their feedback on the circumstellar environment. We propose SOFIA GREAT observations to obtain (velocity-resolved) spectral maps of CII and OI, two lines which are excellent PDR tracers, of four shells produced by young mid-mass stars in a nearby molecular cloud. These lines will allow us to trace the gaseous component that cannot be traced by CO data, yet essential for assessing the total effect of the feedback from mid-mass stars on the circumstellar environment. We will use the proposed SOFIA data to determine the structure of the wind-driven shells, ascertain their effect on the surrounding medium and constrain the wind driving mechanism. Combining the proposed GREAT data with existing molecular line and continuum data, and comparing them with models and MHD simulations of wind-driven shells will allow us to obtain a complete picture of the impact of the radiative and mechanical feedback from mid-mass stars on their parent cloud.
Proposal ID: 06_0199
Principal Investigator: Laura Fissel (National Radio Astronomy Observatory)
Title: Testing Predictions of Dust Grain Alignment Theory in RCW 36 with HAWC+/BLASTPol
Abstract: Major technological advances in telescopes and detectors for submillimeter and far-IR wavelengths are now enabling astronomers to construct vastly improved magnetic field maps for star forming molecular clouds. For example, the P.I. of this proposal led a 2016 paper presenting over a thousand independent measurements of magnetic field direction across the Vela C molecular cloud. Such work exploits the tendency for interstellar grains to become aligned perpendicularly to the ambient cloud magnetic field, which causes their emission to be measurably polarized. A major limitation in interpreting the maps, however, is our uncertainty in the portions of a target cloud containing aligned grains, as we don't fully understand the grain alignment mechanism. Without such knowledge all our magnetic field maps will remain "pretty pictures," of limited value for testing star formation theory. Luckily, magnetic grain alignment theory now allows quantitative predictions, as discussed in a recent Annual Reviews of Astronomy and Astrophysics article led by one of the co-investigators of this proposal (Andersson). For example, it is now possible to predict how the polarization fraction depends on wavelength. We propose to observe this "polarization spectrum'' via observations of the RCW 36 HII region in Vela C, combining new SOFIA far-IR polarimetry with recent balloon-borne submillimeter polarimetry (BLASTPol). Our principal advantages are (a) the high quality of both the balloon-borne and the anticipated airborne data sets, and (b) the simple ring-like geometry of the dense gas that interacts with the bipolar HII region. Our results will provide uniquely powerful tests for grain alignment theory as applied to the dense, massive, and opaque clouds where most stars form.
Principal Investigator: Friedrich Wyrowski (MPIfR Bonn)
Title: The atomic to molecular transition in high-mass star-forming regions
Abstract: Carbon in different phases (C+ C, and CO) plays a key role in the evolution of the ISM as major coolants, and studying them offers a powerful means to examine the physical conditions and energetics of the ISM. With the aim of providing insights into how high-mass stars form and interact with the surrounding ISM, we propose to map the [CII] fine-structure line at 1.9 THz for a representative cloud sample of high-mass star-forming evolutionary phases that we have just successfully imaged in the [CI] 609 micron line with the APEX telescope to probe their atomic carbon content. In combination with available multi-transition CO data our observations will enable us to probe how the physical, chemical, and energetic conditions of the carbon-traced ISM change across evolutionary stages of high-mass star formation, as well as to comprehensively evaluate [CII] mission as a tracer of CO-dark H2.
Proposal ID: 06_0204
Principal Investigator: Benjamin Weiner (Steward Observatory)
Title: Far-IR lines in highly ionized dwarf starbursts: toward understanding high-redshift [C II] and [O III] emission
Abstract: We propose to use FIFI-LS to measure the [C II] 158 µm and [O III] 88 µm fine structure lines in three local metal-poor strongly star forming objects. These are selected to have extreme optical and UV emission, similar to that observed at z>6 and indicating a substantial population of recently formed low-metallicity massive stars, potentially analogous to high-z galaxies. The first ALMA observations of the rest frame far-IR spectra of reionization-era galaxies suggest substantially different gas and dust properties than typically found at lower redshifts. The [C II] 158 micron fine structure cooling line is far weaker than predicted in Lyman-alpha emitters at z>6, and the [O III] line at 88 microns has been detected with an order of magnitude higher flux than [C II]. The detection of strong nebular CIII] and CIV emission in the rest frame UV indicates that the radiation fields of these objects are particularly intense, and suggests that the peculiar far-IR properties may be related to metal-poor gas and intense star formation. However, we have yet to identify a population of galaxies at lower redshift with comparable far-IR emission, making interpretation of these observations speculative. With SOFIA/FIFI-LS observations we will measure the [C II]/SFR and [O III]/[C II] ratios produced by the highest specific-SFR galaxies in the local universe. Combining with HST/COS and optical spectra, we will study in-detail the relationship between the hot young stars and ISM in these extreme objects. These observations represent a critical empirical baseline for interpretation of both ALMA and future JWST observations in the reionization era.
Principal Investigator: Robert Simon (I. Physik. Institut; University of Cologne)
Title: Origin of a Large Arc-like Structure at the Far Side of the X1 Cusped Orbit
Abstract: We have detected a large (~ 8 pc in radius) arc-like structure of unknown origin at the far side of the X1 cusped orbit towards the line-of-sight to the Sgr A Complex. The arc shows up in the sub millimeter [CI](1-0) and CO(4-3) observations in Garcia et al. (2016) and it is found between radial velocities +170 to +190 km/s. Using the unique capabilities for [CII] mapping of the SOFIA observatory, we aim to identify the nature of the excitation source(s) by investigating the line strength spatial variation of the ionized emission, and possible shock signatures originated by the interaction with either massive stars, SNRs, or large-scale turbulence. For this purpose, four targeted positions within and outside the arc are selected for study. Finding a stellar origin of the excitation source would challenge our current understanding of the massive star formation process within the GC, as it is usually thought to occur in the innermost parts of the CMZ, in the X2 orbits, instead of the outer X1 orbits.
Proposal ID: 06_0211
Principal Investigator: Francisco Muller-Sanchez (University of Colorado Boulder)
Title: Testing Unification Models in Dual Active Galactic Nuclei
Abstract: Dual active galactic nuclei (AGNs), which are kpc-scale separation AGN pairs in galaxy mergers, are ideal targets for testing unification models and models of galaxy evolution. By definition, the AGN nature of the two nuclei suggests that they must be consistent with standard unification models (i.e, a dusty torus obscures the central engine in type 2 AGN). At the same time, they are the result of merger-induced nuclear activity. Galaxy evolution models suggest that merger-induced AGNs are heavily obscured for long periods by the high gas densities powering them. Eventually, feedback drives away material, creating a brief window in time in which the AGN is not obscured. Therefore, in these models, there is no need for a small-scale torus. We are constructing for the first time the spectral energy distributions (SEDs) of the two AGNs in dual AGN systems using data from Hubble and Chandra telescopes, in combination with VLA, Keck and VLT data. However, a critical missing component is dust emission at 30-40 microns, which can only be achieved by SOFIA. We propose FORCAST 31.5 and 37.1 microns observations of the complete sample of 5 confirmed dual AGNs with angular separations >3.5". As suggested by current models, the best wavelength to detect thermal emission from a torus would be between 30-40 microns, where both the non-thermal core and the stellar emission sharply decline, and the torus emission peaks. Thus, FORCAST provides 1) the best angular resolution between 30-40 microns of the current suite of instruments, crucial to separate the emission from the two AGNs, and 2) the largest constraining power for torus models, crucial to characterize the properties of the torus in AGNs."
Proposal ID: 06_0214
Principal Investigator: Thushara Pillai (Boston University)
Title: Large Scale Gas Dynamics in Highly Magnetized Filaments
Abstract: A dominant component of the ISM that has received considerable attention is that of filaments which are ubiquitous and might dominate the mass reservoir in molecular clouds. Enormous progress has been made recently towards understanding filament properties in dust emission. The densest filaments are hosts to low and high-mass clusters. In a major step towards understanding the role of magnetic fields in filaments across all relevant spatial scales, we launched a multi-wavelength dust polarization survey called POLSTAR. POLSTAR covers three major classes of filaments: (i) Pristine (ii) Hub-Filament systems and (iii) Perturbed. Filaments are not isolated entities. They are embedded in and dynamically connected to their large scale environment. The submm polarization probes only the densest portions of the filaments. Kinematic information in the form of dense gas tracers exists on the same sub-pc scales. Our near-IR and far-IR polarization observations probe the large (parsec) scale structures around filaments. Unfortunately, though, we have not been able to probe the kinematics of this gas on larger scales to date. Since CII has now shown to be a major mass tracer that can reliably probe the envelope of clouds, we propose a comprehensive CII mapping of parsec scale structures around POLSTAR filaments at 1.9 THz to fill this crucial gap. With this combined dataset we will probe the accretion and gas kinematics from lowest to the highest densities in filaments. This will for the first time systematically establish the total mass reservoir as well as a direct relation between accretion flows, gas dynamics and magnetic fields in filaments at different stages of evolution and hence prove to be an important cornerstone for filament research in the coming decade.
Proposal ID: 06_0215
Principal Investigator: Matthew Richter (UC Davis)
Title: H2O absorption toward Orion KL: Improving on ISO
Abstract: The ability to observe H2O is a primary benefit of SOFIA. Because of interference from Earth’s atmosphere, much of what we know regarding H2O absorption and emission in celestial objects comes from the limited number of previous space missions such as ISO. Therefore, our knowledge of even very well-studied environments such as the Orion BN/KL IRc region is limited by the constraints imposed by those observatories. With SOFIA/EXES, we can drastically improve on aspects of ISO observations. We propose to map the BN/KL region at the spatial resolution limit of SOFIA to examine in detail rotational H2O lines at 26 and 27 microns seen in a single spatial pixel by ISO. With these data, we can study the spatial distribution of the lines, look for line profile variations, and investigate the abundance and temperature variations that are likely present across such a complicated region.
Principal Investigator: Claudia Comito (I. Physikalisches Institut; Universität zu Köln)
Title: Far-infrared determination of the oxygen gradient across the Galaxy
Abstract: Atomic oxygen functions as main coolant in diffuse atomic and molecular clouds, a feature that makes its presence crucial for star-formation processes. State-of-the-art 3D-MHD simulations can reproduce the life cycle of molecular clouds within the ISM, but rely heavily on a robust knowledge of the oxygen abundance across the Galactic disk. What we know on the distribution of atomic oxygen in the Galaxy is based on UV and near-IR spectroscopy of stellar photospheres. Recently, high-spectral-resolution observations of the ground-state fine-structure transition of OI at 63 micron have been made possible by SOFIA and the GREAT receiver, and atomic oxygen studies based on the ground-state transitions have been initiated. The goal of our project is to expand our sample and attempt to derive a gradient of oxygen abundance as a function of Galactocentric radius, based on observations of the 63-micron OI line in the atomic and diffuse molecular gas towards 5 previously unobserved (at 4.7 THz) sightlines. Our results will allow to test the dependence of the formation process of molecular clouds on the chemical composition, a topic which has only recently begun to be explored with numerical MHD simulations.
Proposal ID: 06_0218
Principal Investigator: Diane Wooden (NASA Ames Research Center)
Title: FORCAST Observations of a CY6 ToO Comet
Abstract: A bright Target-of-Opportunity comet provides an important opportunity to obtain high SNR FORCAST spectra that cover the mid- and far-IR wavelengths of the crystalline silicate features to assess the crystalline fraction (f_cryst), to identify spectral resonances from not only Mg-rich crystalline silicates but also to search for those from Fe-rich crystalline silicates, and to search for signatures of cometary organics. Cometary f_cryst is a critical benchmark for models of radial transport in our protoplanetary disk and for understanding the earliest stages of planet formation. Forsterite crystals (MgSiO4) are detected in most comets, and infrequently enstatite (MgSiO4). Mg-rich crystals are thought to be condensates from the gas-phase. Fe-rich (>20% Fe) crystalline silicates are abundant in Stardust samples, in some giant chondritic porous IDPs, and are present in UltraCarbonaceous Antarctic MicroMeteorites (UCAMMs). The minor element abundances (Mn, in particular) in the Fe-rich olivine crystals demonstrate they are type II chondrule fragments or micro-chondrules - they are crystals formed by the rapid-cooling of melts and are not condensates like the Mg-rich crystals in comets. Some comets have a wider diversity of type II chondrules than found in all carbonaceous chondrites combined! The mystery is that the spectral features of Fe-rich crystals have yet to be identified in the IR spectra of comets. f_cryst is derived for 17 comets, with only 5 of which are Oort cloud comets. Expanding the database of comets for which the SNR is high enough to determine f_cryst and to search of features from Fe-rich crystals (which are notably shifted to the red compared to Mg-rich crystals) and organics is of considerable scientific value. Seven out of 10 of the brightest comets of the last two decades have been ToO comets, many being dynamically new Oort cloud comets. Only FORCAST can produce a legacy 5--27 micron data set for a bright (~0.43 Jy @ 10.4 µm) CY6 ToO comet.
Principal Investigator: Juergen Wolf (Deutsches SOFIA Institut; Universität Stuttgart)
Title: Stellar Occultations by Trans-Neptunian Objects and Centaurs
Abstract: Our solar system beyond Neptune's orbit is populated with numerous small objects, referred to as Trans-Neptunian Objects (TNOs). More than 1800 TNOs are known today ranging in size from the most prominent one, Pluto (2370 km diameter), down to a few tens of kilometers. Most diameters have been determined by radiometric methods in the IR/FIR (Spitzer, Herschel) with uncertainties in the 20% range. Only for Pluto and about 12 other objects have the projected diameters been measured more accurately by stellar occultations. A group of objects lingering between the orbits of Jupiter and Neptune, the Centaurs, are believed to have originated from TNOs. Two of them, Chariklo and Chiron, have recently drawn attention, as stellar occultations have revealed rings around them. Our proposed occultation observations with SOFIA shall add to the sparse knowledge on TNOs and Centaurs by determining more projected diameters and albedos. They have the potential of detecting moons, rings and atmospheres. We will use SOFIA's demonstrated capability of measuring occultations (Pluto 2011 & 2015) with its Focal Plane Imager (FPI+) to observe up to five events on flight legs of approximately 30 min each. As most of these events cannot be predicted accurately enough more than a few months or weeks ahead of time, we propose these as targets of opportunity.
Proposal ID: 06_0221
Principal Investigator: Ranga-Ram Chary (Caltech/IPAC)
Title: Measuring the Spins of Supermassive Black Holes Through High Cadence Optical Imaging
Abstract: The spin of a black hole is a fundamental quantity, like its mass. Measuring the spin of supermassive black holes (>1E6 Msun) has thus far only been possible in the X-rays, through the gravitational redshift of the Iron Kalpha line and is limited to about 10 galaxies which are adequately bright. The requirement on X-ray brightness biases the spin measurement since for a black hole to be bright, it needs to be rapidly accreting, a process which intrinsically spins up the black hole. Furthermore, the X-ray results on spins are model-dependent, typically requiring a parameterization for the unknown inclination of the accretion disk and the location of the illuminating corona. We have demonstrated a technique using Palomar/CHIMERA which leverages 1-second cadence, optical imaging to constrain the innermost stable orbit of an accreting particle which in turn is related to the spin of the black hole. Here we propose to target two Southern hemisphere targets with SOFIA/FPI+ which have the best measured X-ray spins but are inaccessible from Palomar. The goal of our observations is to verify consistency between X-ray spin measurements and optical spin measurements, breaking the uncertainty in X-ray spins associated with inclination, constraining the time variable component of emission from the accreting black hole and thereby distinguishing between two competing scenarios for the growth of supermassive black holes.
Proposal ID: 06_0222
Principal Investigator: Tommy Wiklind (Catholic University of America)
Title: Using SOFIA to Study Local High-z Analogs
Abstract: This proposal aims at deriving the star formation history (SFH) and characterize the ionized interstellar gas of a sample of nearby star forming dwarf galaxies. The galaxies are selected from the Brown et al. (2014) UV-to-MIR spectroscopic sample. The galaxies in this proposal are the ones from the Brown et al. sample that successfully fit broad-band photometric data of high redshift galaxies (z>4) and, hence, are potential local analogs of high redshift galaxies. A primary constraint for defining a local analog is that it does not exhibit an extended star formation history. One of our aims is to define the maximum age of the SFH of the galaxies in our sample. Preliminary results for three galaxies suggest that they are truly young objects. We will use the HAWC+ instrument, covering all available filter to derive the far-infrared spectral energy distribution. From this we derive the total FIR luminosity which is needed to constrain the attenuation and derive the SFH. We will use FIFI-LS to observe the [CII] 158µm and [OIII] 88µm fine-structure lines in four galaxies in our sample that do not have Herschel data. These lines are accessible with ALMA for high redshift objects and can be used to characterize the ISM. This proposal is the major part of a multi-wavelength study of the local star forming dwarfs. We are also obtaining the distribution and kinematics of the neutral atomic gas through 21cm observations. This is a Thesis Enabling Proposal. The SOFIA observations constitute the major part of a PhD student thesis work.
Proposal ID: 06_0223
Principal Investigator: Jian-Yang Li (Planetary Science Institute)
Title: Determining the Mineralogical Evolution of Asteroid (145) Adeona through Degree of Aqueous Alteration to Support Dawn Extended Mission
Abstract: NASA’s Dawn mission is preparing an extended mission to perform a slow flyby of a Ch-type asteroid (145) Adeona in September 2019 to study the evolution and differentiation processes occurred on primitive type planetesimals. Only limited data are currently available to constrain the surface composition of this target. The existence of the 0.7-Âµm absorption feature suggests that Adeona must have undergone aqueous alteration early in its history. Therefore the degree of aqueous alteration is an important indicator for its initial composition and temperatures experienced in its interior. Mid-infrared has been shown to be the most diagnostic spectral region to determine the degree of aqueous alteration. We hereby request a total of 0.5 hours of SOFIA+FORCAST time to observe Adeona during its February/March 2018 observing window to obtain low-resolution spectrum through G111 and G227. The required instrument configuration is only available through SOFIA-FORCAST. The upcoming February/March 2018 observing window will be near Adeona’s perihelion and thus is the best opportunity, and the next window in May 2019 is close to the Dawn’s planned flyby and would make it tight to feed the results to the mission planning, necessitating our proposed Cycle 6 observations. Our primary science goal is to determine the mineralogical evolutionary state of this asteroid through the degree of aqueous alteration. In combination of future observations, our proposed observations will also serve a secondary goal of characterizing the possible mineralogical heterogeneity on the surface of Adeona. Our proposed observations are important to support the design and planning of the Dawn extended mission. These observations also provide complementary data that help the interpretation of the Dawn data expected to collect during the flyby, and put the Dawn results into the broad context of the formation and evolution of primitive type asteroids in general.
Proposal ID: 06_0225
Principal Investigator: Gordon Stacey (Cornell University)
Title: FIFI-LS Spectroscopy of Nearby IR Bright Galaxies: Tracing Stellar Populations, the O/N Abundance Ratio, and Absolute Abundances
Abstract: We propose to continue our program to map the [OIII] 52 µm line emission from the central regions of IR bright, nearby star forming galaxies including both normal and low metallicity systems. These data will be used together with Herschel/PACS [OIII] 88 µm, [NII] 122 µm, and [NIII] 57 µm emission line data and hydrogen radio recombination line interferometric observations to constrain the ionized gas density and mass, the hardness of the stellar radiation fields (hence most massive star on the main sequence), the O/N ratio (which reflects the numbers of cycles for star formation) and the absolute ionize gas phase N/H and O/H ratios which reflect the star formation efficiency integrated over time. We will also use the Herschel archival [OI] 63 and 146 µm, and [CII] 158 µm imaging which enables us to characterize the neutral ISM and the strength of the FUV (6-13.6 eV) stellar radiation fields. In this way, we will have a continuous measure of the stellar UV radiation fields from 6 to 54 eV thereby constraining the numbers of upper main sequence stars. The proposed FIFI-LS [OIII] 52 µm line observations are the lynch-pin that holds the technique together. These measurements provide a local benchmark for our line-ratio techniques that can be applied to similar studies of high-z galaxies where it is expected that stellar radiation fields will be harder, and the O/N radio will be larger for the lowest metallicity galaxies. Therefore, the proposed observations are fundamentally important to our understanding of the star formation process over cosmic time.
Proposal ID: 06_0226
Principal Investigator: Loren Dean Anderson (West Virginia University)
Title: Disentangling [CII] Emission toward HII Regions
Abstract: The 158 µm [CII] line is the most important coolant of the interstellar medium (ISM) and its strength is highly correlated with the star formation rate (SFR) of galaxies. It emits strongly in HII region photodissociation regions (PDRs), from ionized gas, and from neutral material. Because of projection effects, the fraction of [CII] emission thought to arise from ionized gas has not been accurately measured, and we therefore lack crucial information necessary to understand the [CII]/SFR connection. We will make [CII] maps of 10 HII regions using the upGREAT heterodyne receiver array and, with the help of simulations, will determine the fraction of [CII] emission that arises from HII region PDRs, ionized gas within the region, and the local warm ionized medium. By sampling a variety of HII regions in different evolutionary stages across the Galactic disk (at a range of metallicities), these results will be generalizable to the entire Galaxy. Additionally, we will establish correlations between [CII] emission and various other tracers of star formation, and will search for trends in these relationships with HII region evolutionary stage and Galactic location. We took SOFIA data of the HII region complex S235 in Cycles 4 and 5 as a pilot program for the present study. The proposed observations will provide much-needed information on how the [CII] line traces the SFR, and will provide valuable insight for future studies with ALMA.
Principal Investigator: Helmut Wiesemeyer (Max-Planck-Institut für Radioastronomie)
Title: Oxygen production and transport in the Enceladus gas torus
Abstract: Context: Magnetospheric events in planetary environments are highly dynamical phenomena. They reach from star-planet interactions to the variety of chemical and physical processes known from the magnetospheres of Earth, Jupiter and Saturn, which are replenished by injections of gaseous and also solid matter. Several generations of in-situ probes answered many long-lasting questions, but also revealed unexpected problematics. To date, follow-up studies with earthbound and airborne observations have not yet fully explored their potential to shed light on these issues. They would greatly improve our understanding of the enrichment of planetary environments by agents like volcanic or geothermal activity, best known from Jupiter's Io and Saturn's Enceladus, respectively. Aims: Owing to the hot spot activity near its south pole, Enceladus supplies a neutral gas torus centered on its orbit with matter (water, methane, CO, CO2, N2, and ices). Subsequent impact- and photoionization and charge exchange reactions provide heavy ions that are accelerated in Saturn's magnetosphere, making its mass load (relative to the magnetic field) the heaviest in the solar system. This particle flux is modulated at the planet's rotation period, yet the dipole component of Saturn's magnetosphere is aligned with the planet's rotation axis (unlike the Jovian magnetosphere). We propose to address this puzzle by spectroscopic mapping of the 63 micron and 146 micron lines of the fine-structure triplet of OI of which the abundance is tightly related to that of water (the former being an impact- and photodissociation produce of the latter), and to that of OII, thanks to a charge transfer reaction. Methods: The high-frequency array (HFA) aboard SOFIA is currently the only instrument allowing us to pursue this investigation with the required velocity resolution. Its derotator will be used to adjust the hexagonal footprint of the HFA to the orientation of Saturn's rings. Anticipated results: Spectra of the OI fine structure lines at various positions in the Enceladus gas torus, resolved in velocity and, for southern hemisphere observations, in time.
Proposal ID: 06_0234
Principal Investigator: Brian Svoboda (University of Arizona)
Title: A Systematic Survey of Magnetic Field Orientation in Massive Quiescent Clumps
Abstract: Context: High-mass stars play dominant roles in the evolution of the ISM. However, the physical mechanism that drives the growth of high-mass protostars and protoclusters, especially the role of magnetic fields in this process, remains an open problem. Aims: We have assembled a robust and representative sample of the highest mass Galactic molecular cloud clumps with at less than 5 kpc and which are quiescent with no evidence of high-mass protostars from Galactic plane IR-radio surveys. MHD simulations suggest the perpendicular alignment of magnetic fields with dense gas structures is caused by converging flows. We shall systematically test this by comparing the relative magnetic field orientation to clump properties and kinematics in systems prior to high-mass protostellar feedback. Methods: Using HAWC+ in band E we shall image spatially resolved linear polarization maps to determine the relative magnetic field alignment with respect to the dense gas structures. Synergies: By comparing to already obtained ALMA millimeter continuum and VLA ammonia data, the magnetic field orientation will be compared in detail to the clump dense core population, fragmentation properties, and dense gas kinematics. Anticipated Results: The magnetic field orientation may provide a powerful constraint on the dynamics of mass inflow feeding the sites of star formation, but cannot yet be applied until it has been systematically compared to clump physical properties and gas kinematics.
Principal Investigator: Anna Parikka (University Cologne)
Title: Formation of brown dwarfs due to photo erosion
Abstract: The origin of brown dwarfs (BDs; M<0.075 Msun) is still under debate. Some models predict that BDs form through turbulent fragmentation as normal stars while other models suggest ejection of substellar mass embryo from multiple protostellar systems and/or fragmented disks. Photo-erosion of prestellar cores due to external radiation from nearby massive stars may be another formation mechanism for BDs. The different scenarios can be tested by studying the earliest phases in BDs formation (proto-BDs), when they are still embedded in the dense cores. We propose velocity resolved mapping of the [CII] emission using the upGREAT Low Frequency Array on SOFIA toward a bright rimmed clump G192.32-11.87 to test the photo-erosion scenario for BDs formation. The datacubes of [CII] emission and additional 63µm [OI] line data will be used to reveal the ionization front of the PDR and to study the effects of the photo-erosion on the formation of the BD G192S and the very low-mass protostellar object G192N in the dense clump G192.32-11.87.
Proposal ID: 06_0237
Principal Investigator: Jan Cami (SETI Institute)
Title: Revealing the formation of fullerenes in planetary nebulae
Abstract: In recent years, it has become clear that our understanding of the formation, excitation and evolution of carbonaceous dust grains and large molecules is incomplete: we do not know the physical conditions and chemical processes that lead to the formation of fullerenes. Here, we propose to use SOFIA to elucidate both the required conditions and most plausible chemical routes towards fullerene formation by determining the strength of the radiation field (Go), the gas temperature T and the density (n) in the PNe environments where fullerenes emit. In planetary nebulae, the fullerene emission originates from the photo-dissociation region (PDR) surrounding the central ionized zone. For PDRs, Go,T and n are routinely determined from four observables: the total infrared flux (FIR), and the observed emission line fluxes of the three dominant cooling lines: [C II] at 158 µm and [O I] at 63 µm and at 146 µm. We therefore propose to measure these four parameters for a sample of fullerene-rich PNe, using FIFI-LS to measure the emission line fluxes of the three main cooling lines, and using HAWC+ to obtain photometric measurements of the dust continuum in the far-IR from which we can calculate FIR. SOFIA is currently the only observatory capable of carrying out these important observations, and providing the required measurements. We will use these measurements as input to PDR codes tailored to the carbon-rich chemistry of these PNe to determine Go,T and n. Knowing these parameters will enable us to pinpoint the conditions and routes to form and excite these stable species. This work will also lead to a much better understanding of the range of conditions under which different molecular and dust components can form and survive, including PAHs and other carbonaceous species.
Proposal ID: 06_0239
Principal Investigator: Sangeeta Malhotra (NASA's Goddard Space Flight Center)
Title: SOFIA's unique FIR view of green peas
Abstract: While ALMA is being used hard to look for [CII] lines from high redshift Lyman-alpha galaxies, it is getting a patchwork of detections and non-detections which are hard to interpret. High redshift Lyman-alpha galaxies have high star-formation surface brightness, and high dust temperatures, which would lower the [CII] flux. On the other hand, low metallicities should lead to higher [CII] line emission. Fortunately, we know of good local analogs of high-redshift Lyman-alpha emitting galaxies - Green Peas. They are also good leakers of the Lyman-continuum needed to ionize the IGM. We propose SOFIA observations of Green Peas to measure [CII] and [OIII] lines. These will be tremendously useful to direct and help interpret ALMA observations of Lyman-alpha galaxies during reionization. With FIFI-LS on SOFIA we will observe [CII] 158 micron, [OIII] 88 micron, and [OIII] 52 micron lines in 6 galaxies. This will enable us to calibrate the star-formation-rate vs [CII] relation for low redshift Green Peas and use that to predict [CII] strengths of high-z LAEs. With both [CII] and [OIII] 88 micron lines, we can check if [CII] or [OIII] 88 micron is a stronger line for Lyman-alpha emitting galaxies. This will be very useful for planning ALMA observations. The ratio of [OIII] (88 and 52 micron) lines will yield ionized gas densities and pressures. We can also test if the [CII]-mid-IR flux correlation stands for these galaxies using WISE measurements.