- SOFIA Overview
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Cycle 8 Selected Proposals Abstracts
Principal Investigator: Goran Sandell (Institute for Astronomy; UH Hilo)
Title: Using [CII] to probe the environment of the LkHa101 HII region, reflection nebula and foreground cloud
Abstract: We propose to use the upGREAT LFA to map ~ a 4.5 arcmin region around the young B0 star LkHa101 in [CII]. The star is in the center of a large reflection nebula NGC1579 and excites the HII region S222. The star is still heavily accreting and has a strong stellar wind. Our goal with these observations is a) to probe the dense PDR we expect to see in the interface between the HII region and the surrounding molecular cloud (at -3.8 km/s), b) investigate the [CII] emission in the surrounding large refection nebula (also at -3.8 km/s and c) characterize the PDR emission of the foreground dark cloud to better understand the physical condition in this unusual cloud. Modeling will be done using simple PDR models.
Principal Investigator: Robert Gehrz (University of Minnesota - Twin Cities)
Title: SOFIA Target of Opportunity (ToO) Observations of Bright Classical Novae in Outburst
Abstract: Classical novae (CNe) contribute to Galactic chemical evolution by injecting dust grains and gas into the interstellar medium (ISM). We have conducted SOFIA Cycle 1, 2, 3, 4, 6, and 7 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 7 with FORCAST to cover the continued development of CNe that became active during Cycle 7 and to initiate coverage of CNe that go into outburst during Cycle 8. 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 LiCNONeMgAl 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 nova that was brighter than 8th magnitude at visual maximum can trigger our ToO program when supporting optical/IR ground-based or space-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).
Principal Investigator: William Reach (USRA)
Title: Extended mass loss from Evolved Stars
Abstract: Context- The largest stars shed most of their mass during late stages of evolution. That mass loss determines their fate (neutron star, black hole) and enriches the interstellar medium (mass loss and supernova). Aims- The extended mass loss (further than 10 stellar radii, tens of thousands of years ago) measures the amount of material lost and whether that mass loss was constant or episodic. Methods- We propose to trace the extended mass loss by mapping the [C II] far-infrared line using GREAT. The stellar material begins molecular but gets photodissociated by the external radiation field, after which point the primary coolant should be the proposed line, as it is in the diffuse interstellar medium. Synergies- Evolved star mass loss is a field with a long history and is of fundamental importance for understanding both the stars themselves and the ISM. Recent observations with ALMA are unveiling the spatial distribution (including shells) of molecules in the recent outflows close to the stars. JWST will dramatically extend our reach to evolved stars in nearby galaxies; those results will measure what we call "extended" mass loss in this proposal. Anticipated Results- The results of our proposed observations will include the first detailed look at the total mass-loss from the irradiated outflow of red supergiant NML Cyg, ultra-high-mass-loss from supergiant VY CMa, high mass-loss AGB stars NML Tau and IRC+10216, and luminous blue variable HD 168625 tracing the extent of ionized carbon as daughter product of CO from the molecular outflows. The result could significantly modify the estimate of total mass-loss from these stars, their original mass, and their enrichment of the ISM.
Principal Investigator: William Langer (JPL/Caltech)
Title: Dynamics and Ionization of the Orion Bar HII-PDR Interface Traced with [NII]
Abstract: We propose to study the dynamics of the interaction of the ionized and neutral gas in the Orion Bar region with spectrally resolved [N II] 4GREAT maps at 205 microns. A PACS survey of the [NII] 122-micron line in the Orion Bar shows strong emission, with a different distribution of N+ compared to C+ and O. However, PACS data are spectrally unresolved and do not trace the dynamics of the HII-PDR interaction resulting from the high intensity UV field. We will map a 4’x4’ region of the Orion Bar in the [NII] 205-micron line with upGREAT. The [NII] 205-micron spectral maps will allow us to derive the electron density and its velocity structure in the HII region, by combining the it with H41alpha radio recombination line (RRL) maps using a technique we developed for deriving the electron density with these ion tracers. The electron density is a direct probe of the HII-PDR interaction and the role of radiation fields on clouds which is critical to understand cloud formation and destruction. Our objective is to understand how HII-PDR dynamics influence the gas properties of star formation sites by comparing observations with models of HII-PDR interactions. We will characterize the structure, properties, and dynamics of the HII-Orion Bar by combining the [NII] 4GREAT and existing IRAM 30m RRL maps, the [CII] upGREAT map, [OI] surveys, which traces the neutral PDR, and molecular gas tracers (e.g. CO). We will use HII-PDR static and dynamical codes to analyze the impact of massive star formation and large UV radiation fields on cloud dynamics. The resulting picture will inform models of cloud formation and destruction necessary to understand massive star formation and the baryonic lifecycle throughout the Milky Way and external galaxies. A version of this proposal was approved for Cycle 7 with Priority 3, we are resubmitting a slightly revised version in anticipation that little, if any, of the original request will be fulfilled. The time requested is 11.13 hours.
Principal Investigator: Enrique Lopez-Rodriguez (SOFIA Science Center)
Title: SOFIA heralds a new era of measuring the magnetic fields of galaxies
Abstract: The evolution of galaxies is controlled by a delicate interplay between gravity, turbulence, feedback, and magnetic fields. Although most current empirical and theoretical approaches to understanding this interplay are mainly focused on gravitational forces, magnetic fields indeed play a fundamental role in the interstellar medium (ISM), galactic dynamics, galactic winds, and intergalactic medium (IGM). However, a self-consistent description of the interplay between the multiphase ISM gas and magnetic fields is still not an integral part of observational or theoretical descriptions of galactic evolution. Our team has made important and unexpected discoveries about the role of the magnetic fields in nearby galaxies. We have found a) that galaxies typically host large-scale and coherent magnetic fields along the spiral arms, b) magnetic field strengths of ~uG with similar contributions from the random and ordered field components, and c) magnetic fields oriented along galactic outflows that are likely responsible for magnetizing the IGM. To date, these results have mostly emerged from single wavelength regimes: radio synchrotron polarization tracing the large-scale field structure in the ionized gas, and optical studies to investigate the effect of scattering and/or extinction by the ISM. These studies access the field on vastly different spatial scales and within different ISM phases. However, the effect of magnetic fields in dense regions of the ISM, outflows, and the ISM of merging galaxies are still poorly described. SOFIA/HAWC+ is key to provide a complete picture using far-infrared (FIR) polarimetric observations. This Joint Legacy Program aims to construct a comprehensive empirical picture of the magnetic field strength and structure in multiphase ISM of galaxies. Using HAWC+, we will conduct a FIR polarimetric survey covering the full disk of nearby galaxies. For the first time, we will combine these results with our radio polarimetric and optical spectroscopic observations to obtain magnetic field strength/structure and gas dynamics as a function of host galaxy properties and kpc-scale galactic environment. The wide-field, multi-wavelength polarimetric observations from this Legacy Program will be a transformative leap that will establish the foundational framework of the kpc-scale magnetic field structure in the molecular gas disks of nearby galaxies.
Principal Investigator: Dariusz Lis (JPL/Caltech)
Title: D/H Ratio in Cometary Water: Understanding the Origin of Earth's Oceans
Abstract: Comets contain some of the most pristine materials left over from the formation of the Solar System. Measurements of the D/H ratio in cometary water provide key constraints on the origin and history of water in the Solar System, and the contribution of comets to Earth's oceans. The 4GREAT instrument on SOFIA now allows very accurate measurements of the D/H ratio through nearly-simultaneous observations of the low-energy rotational lines of HDO at 509 GHz HDO and H218O at 547 GHz. We will use this instrument to measure the D/H ratio in a TOO comet with activity level comparable to that of comet 46P/Wirtanen in December 2018. The data analysis and interpretation will follow the procedures successfully applied to our observations of comet Wirtanen, in which a terrestrial D/H ratio was measured by SOFIA. The same well-tested excitation models will be used to convert the observed line intensities to molecular production rates. Only SOFIA allows nearly-simultaneous observations of the low-energy HDO and H218O in a very similar field of view. This significantly simplifies the analysis and decreases measurement uncertainties. Based on historical average, we expect about one comet per year to be bright enough for HDO to be detectable with SOFIA. Over its remaining lifetime, SOFIA can thus double the number of existing D/H measurements, significantly improving the statistics and providing key observational constraints for understanding Earth's habitability. This research is perfectly aligned with the strategic objective of the DISCOVER theme of the NASA 2018 Strategic Plan: "Understand the Sun, Earth, Solar System, and Universe." The latest Planetary Decadal Survey Vision and Voyages explicitly identified "determining the deuterium/hydrogen and other crucial isotopic ratios in multiple comets" as key measurements for understanding Solar System beginnings.
Principal Investigator: Enrique Lopez-Rodriguez (SOFIA Science Center)
Title: SOFIA/ALMA Survey of Active Galactic Nuclei
Abstract: The immediate surroundings of an active galactic nuclei (AGN) hide the direct signatures of accretion activity along certain lines of sight. The torus is the immediate source of fuel for both accretion and outflow, and is considered the interface between the AGN and their host galaxies within a typical region of a few pc in size with a gas and dust flow cycle. Our team has found that by sampling the wavelength range where the torus emission peaks, we can put tight constraints in the torus properties, e.g. sizes, angular width, number od clouds. Specifically, we have used 30-100 µm FORCAST/HAWC+ observations to trace the warm dust in the torus. We found that the torus size depends on dust temperature (wavelength), that the 10-20 µm emission is mostly in the polar direction at scales of hundred of pc, and that the 432 µm observations well-traced the dust distribution of the torus. The combination of 1-20 µm from ground-based telescopes, 30-100 µm from SOFIA, 70-500 µm from Herschel, and sub-mm from ALMA allow us to disentangle the several emitting components in the central few hundred pc of AGN. We propose SOFIA observations of new 19 AGN located mostly to study the lower-end of the bolometric luminosities. With these new observations, we will have a total of 39 Seyfert galaxies observed with SOFIA within the whole range of bolometric luminosities (log(Lbol [erg/s]) =[42, 46], D = [10, 70] Mpc), AGN types and fully sampled in the 1-900 µm wavelength range. These new observations are part of a currently awarded ALMA proposal that will be able to resolve the torus of the objects in this proposal. These complete SEDs will allow us to compute 2D torus images to study differences in the emission and cloud distribution of the torus in Seyferts and compare directly with the resolved images by ALMA. This approach will allow us to break degeneracies in torus models by disentangle the several competing emission components in the central hundred pc through sophisticated decomposition of the nuclear IR (1-500 μm) SED of AGN developed by our team.
Principal Investigator: William Langer (JPL/Caltech)
Title: Unveiling the Energetics of a LIRG with [CII] and [NII] Spectroscopy
Abstract: Active galactic nuclei (AGN) are among the most luminous sources of galactic radiation, emitting much of their energy in the Far-infrared (FIR) and Mid-infrared (MIR). The source of their energy are massive star formation and the accretion disk surrounding a supermassive black hole. These produce copious amounts of UV and X-ray radiation which create a wide array of ionization states of metals such as carbon, nitrogen, and oxygen, some of which have fine-structure transitions in the FIR and MIR. These fine structure transitions are important probes of the gas, especially the ionized gas in the nuclei and disks. Herschel PACS and SPIRE, and Spitzer IRS detected many of these spectral lines, but the angular resolution of these instruments was too large to resolve even the closest AGN. Furthermore, these instruments lacked the spectral resolution to separate out velocity components. In contrast, interferometric observations resolve these nuclei both spatially and spectrally with observations of molecular transitions such as CO and HCN. However, these only trace the neutral molecular gas. We propose to circumvent these low angular resolution FIR observations using the spectral information in [CII] and [NII] as observed with upGREAT and 4GREAT to identify spatial features by association with velocity information in the interferometric maps. We will observe the nearest luminous infrared galaxy (LIRG) NGC 1068 (at 15.9 Mpc) using OTF [CII] mapping with upGREAT and three pointed [NII] observations with 4GREAT. By identifying the sources of ionized gas within the nucleus and disk we can more effectively interpret the larger data set of PACS, SPIRE, and IRS observations of lines such as [OIII], [OIV], and [NIII]. We will use X-ray dominated region and radiative transfer codes to interpret the conditions in NGC 1068. On a larger scale this approach can impact our understanding of AGNs at larger distances. Time requested is 8.12 hours.
Principal Investigator: Jorge Pineda (Jet Propulsion Laboratory)
Title: What is the Source of the Ubiquitous Dense Ionized Gas Throughout the ISM and Does it Impact [CII] as an SFR Tracer?
Abstract: Herschel and SOFIA [NII] observations have revealed the presence of a ubiquitous dense ionized gas component in the Galactic plane. This medium can be the dominant source of [CII] and [NII] emission in galaxies, and thus its characterization is important for the interpretation of observations of these lines in distant galaxies and for characterizing the UV energy sources in galaxies. Aims: We propose to use FIFI-LS on SOFIA to observe the [NIII] 57μm line along 8 lines–of-sight that have been observed in [NII] 205μm and 122μm, [CII], and hydrogen radio recombination lines. These data will be used to constrain the EUV radiation field and determine the total nitrogen abundance as a function of Galactocentric distance. Synergies: The [NIII] 57μm observations will be combined with a multi-wavelength set of observa- tions including Herschel, SOFIA, NASA’s Deep Space Network 70m antenna, and the Green Bank Observatory. The proposed work will also provide important constraints to theoretical models on the ionization sources in the Galaxy and the formation and evolution of the Milky Way. Anticipated Results: We will combine the [NIII] 57μm observations with those of [NII] 205μm and 122μm to measure the abundance of the two ionization states. We will then be able to determine the strength of the extreme ultraviolet (EUV) radiation field required to explain this ratio of ionization states. This quantity will distinguish among different models proposed to explain the dense ionized gas and evaluate the role of EUV in galactic evolution. Additionally, we will use this data set, and that of [NII] 205μm and 122μm and hydrogen recombination lines, to determine the total nitrogen abundance relative to hydrogen as a function of Galactocentric distance. This abundance ratio is an important quantity for understanding the star formation history of the Milky Way, and to constrain models of its formation.
Principal Investigator: Pak Shing Li (Department of Astronomy; University of California at Berkeley)
Title: The Role of Magnetic Fields in the Formation of Starless Cores in Filamentary Molecular Clouds
Abstract: In the past few years, several attempts have been made to resolve the central regions and possibly detect multiplicity in starless cores. Recently Caselli et al. (2019) have reported the detection of substructure in the central 1000 AU region of L1544. In ALMA Cycle 6, we detected substructures in the central regions of four starless cores, including G208.68-19.20 and G209.29-19.65 in the Orion complex at 1" FWHM, corresponding to a scale of 400 AU. In order to study the role of magnetic fields in the formation of high density starless cores, where stars form, we need information on the physical environment around such cores, which are usually connected with filamentary substructures inside molecular clouds. We propose to observe the polarization in two ~ 1 pc regions of filamentary molecular clouds surrounding the two starless cores G208.68-19.20 and G209.29-19.65 using HAWC+ at Band E to reach a resolution ~ 7000 AU at a distance of 400 pc. With our upcoming ALMA polarization observation focusing on these two cores at the resolution of 400 AU, we shall have an accurate picture of the magnetic field structures from inside the starless core to a region of about 1 pc surrounding the cores. Using our high resolution density and line-of-sight velocity information from NRO 45 m and ALMA Cycle 6 observations, we can infer the dynamical state of their environments. By comparing with the dense cores formed in our high resolution simulations of the formation of filamentary dark clouds, we shall determine what triggers the formation and fragmentation of dense starless cores in filamentary clouds and how these cores evolve. This combination of SOFIA observations, ALMA and NRO observations, and numerical simulation will provide crucial insights on the process of star formation, with implications for the star formation rate and the origin of the stellar initial mass function.
Principal Investigator: Curtis DeWitt (USRA/SOFIA)
Title: Resolving water vapor absorption in the circumstellar disks of FU Ori stars
Abstract: FU Ori and V1057 Cyg are archetypal FUor objects, a class of young, low-mass stars defined by massive accretion events causing 4-6 magnitude brightness increases. Because of the disk heating, these sources have a disk photosphere that dominates the system luminosity, with the observed effective temperature and absorption line width depending on the wavelength of the observation. FUor present a unique opportunity to probe young disk atmospheres because of their unusual disk vertical temperature profile. Using R=100 spectroscopy with IRS/Spitzer, Green et al. 2006 report the appearance of water vapor absorption bands in FU Ori, V1057 Cyg and in other FUors. We will confirm this identification with EXES in medium resolution mode and resolve individual water vapor lines, which will unveil the kinematics and temperatures of the absorbing gas. By comparing the results of two FUors with different luminosity decay timescales, we will begin to investigate the evolution of disk chemistry following rapid accretion events.
Principal Investigator: David Neufeld (Johns Hopkins University)
Title: Kinematics of shock-heated H2 with EXES, and the conversion from para- to ortho-H2
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. A Cycle 6 program, conducted with the EXES instrument toward HH7, has recently carried out velocity-resolved observations of the mid-IR H2 emission lines that dominate the emission from shocks propagating in molecular gas. These observations revealed, for the first time, the presence of velocity shifts between lines of ortho-H2 [S(5) and S(7)] and those of para-H2 [S(4) and S(6)], bearing witness to the conversion of para-H2 to ortho-H2 within the shock wave, and providing among the best evidence yet obtained for the existence of C-type shock waves in which the flow velocity varies continuously. We will follow up our discovery of H2 ortho-para velocity shifts in a single source in Cycle 6, with observations of the H2 S(4) – S(7) emission lines from 6 additional shocked regions that span a range of astrophysical environments including supernova remnants and protostellar outflows. By interpreting the observations in the context of state-of-the-art shock models, we will place unique constraints on the physics of molecular shocks.
Principal Investigator: Paul Goldsmith (Jet Propulsion Laboratory)
Title: Probing Stellar Feedback at cloud boundaries using [OI] observations in SOFIA Data Archive
Abstract: Here we propose to study stellar feedback at cloud boundaries through the kinematics and luminosity of [OI] emission and determine the gas-phase oxygen abundance in warm atomic/molecular regions. Observations of atomic oxygen fine structure line (hereafter [OI]) emission are invaluable in astronomy, since this emission traces exclusively stellar feedback to molecular clouds, which in turn regulates star formation and drives galaxy evolution. The [OI] lines also provide valuable information about the oxygen abundance in high-density regions, which controls the formation of water (Van Dishoeck, Herbst, & Neufeld 2013), an essential molecule for life. However, velocity-resolved [OI] observations are very rare compared to the observations of major atomic and molecular species, (e.g. CO and HI) since the [OI] emission is only observable using suborbital or space telescopes. To date, SOFIA observations of [OI] represent the largest body of velocity-resolved [OI] data. This large data set can make a significant impact on astronomical studies. The proposed program will study [OI] kinematics and the gas-phase oxygen abundance using the large set of SOFIA [OI] spectral maps. These data are all currently in the SOFIA Science Archive. We will focus on the bright star-forming regions observed in both [OI] 63 µm and 146 µm using the SOFIA GREAT and upGREAt instruments. To probe the stellar energy input to the surface of molecular clouds, we will compare the [OI] spectra to the [CII] and CO spectra. This will reveal the unique dynamics of the PDRs (turbulence and gas flows using the [OI] linewidth and skewness) and highlight processes such as photoevaporation and radiation stripping. We will also carry out PDR modeling and the model will provide a relation between thermal pressure Pth and the FUV flux G0, P_th∝ G_0^α, where α is a free parameter describing the relation and determined by the physics of the HII region and PDR.
Principal Investigator: Cristian Guevara (I Physikalisches Institut)
Title: [12CII]/[13CII] isotopic abundace ratio in M17SW and NGC 1977
Abstract: Our observations with the 14 pixel SOFIA/upGREAT receiver of the [12CII] fine and [13CII] hyper-fine structure lines have shown that the [CII] is heavily affected by self-absorption effects and/or high optical depth. The observations were done at very high velocity resolution and sensitivity towards four PDRs in the Galaxy, with M17 the one with the most prominent feautures. This scenario can be explained with a double layered model, with a high density [CII] background layer in emission, absorbed by a cold, lower density foreground [CII] layer. Both, the extremely high column densities of the warm emitting gas and even the nature of the colder foreground absorption gas, are very hard to explain in the context of standards PDR models. A key element for this analysis is the [12CII]/[13CII] abundance ratio. The abundance ratio allows us to scale up the [13CII] line and therefore, transform it to an equivalent optically thin [12CII] emission. This equivalent emission is compared to the observed [12CII] line, for deriving the optical depth and the physical properties of the gas. We have assumed that the [12CII]/[ 13CII] isotopic abundance ratio is the same than the 12C/13C elemental abundance ratio but this is not necessarily true. Fractionation effects could arise and increase the abundance ratio. The high sensitivity of GREAT now allow us to directly derive the [12CII]/[13CII] isotopic abundance ratio from the comparison of the line wing emission of both isotopes through deep integrations and to detect fractionation signs if present. Neither measurements of the carbon isotopic abundance ratio nor detection of fractionation for [CII] has ever been done before. We have selected two regions for this analysis, M17SW and NGC 1977. Both regions present high optical depth for the [CII] line and an edge-on structure. Both regions has different physical conditions, these differences allow us to address posible dependencies of the fractionation on the environment.
Principal Investigator: David Neufeld (Johns Hopkins University) and Peter Schilke (University of Cologne)
Title: HyGAL: characterizing the Galactic interstellar medium with hydrides
Abstract: By means of absorption-line spectroscopy towards 22 background terahertz continuum sources widely distributed within the Galactic plane, we will obtain robust measurements of the column densities of six hydride molecules (OH+, H2O+, ArH+, SH, OH and CH) and two key atomic constituents (C+ and O) within the diffuse ISM. Recent studies with Herschel have demonstrated the unique value of specific hydride molecules as quantitative diagnostic probes of the H2 fraction, the cosmic-ray ionization rate, or of “warm chemistry” associated with the dissipation of interstellar turbulence in regions of elevated temperature or ion-neutral drift. These observations will allow us to address several related questions: (1) What is the distribution function of H2 fraction in the ISM? (2) How does the density of low-energy cosmic-rays vary within the Galaxy? (3) What is the nature of interstellar turbulence (e.g. typical shear or shock velocities), and what mechanisms lead to its dissipation? Because of atmospheric absorption, the transitions to be observed in this program are inaccessible from the ground and can only be observed from airborne or satellite observatories. Our investigation is synergistic with ancillary observations of non-hydride molecules that have been/will be performed with ALMA, JVLA, the IRAM 30 m telescope, and APEX. There is a very timely synergy with theoretical models for H2 formation within the turbulent ISM, several of which are under development by groups within our team. The anticipated results are (1) a determination of the distribution function for the H2 fraction in the Galaxy, and how it varies; (2) a determination of the cosmic-ray ionization rate and how it varies; (3) an improved characterization of turbulence in the diffuse ISM, and its dissipation; (4) the provision of enhanced data products that will serve as a legacy for future ISM studies.
Principal Investigator: Rolf Guesten (MPI Radioastronomie)
Title: GREAT/SOFIA follow-up observations to our recent detection of HeH+
Abstract: After multiple unsuccessful searches carried out over a period of three decades, recent observations with the GREAT spectrometer on SOFIA have led to the first astrophysical detection [Guesten et al. 2019] of the helium hydride molecular ion [HeH+]. This simple ion - first formed at a redshift z ~2000 by the radiative association of helium atoms with protons - was the very first molecule to form in the history of the Universe, according to models for the chemistry of primordial gas [e.g. Galli & Palla 2013]. Our recent detection of HeH+ [Nature 568, 357] was obtained by SOFIA/GREAT toward the planetary nebula NGC 7027, by means of high-spectral resolution observations of its J = 1-0 pure rotational transition at 149.13 µm. Using the most current reaction rates for the destruction and formation processes of HeH+, notably our (Cloudy) model predictions fall short of the observed fluxes by factor 8. We consider possible shortcomings (source geometry of our NGC70217 model, too low radiative association rate), pointing out implications of an order of magnitude enhanced HeH+ abundance for the evolution of the early Universe. To further constrain our models (and the reaction rates) we suggest observations of two additional high-excitation PNe (NGC6357 and NGC6302).
Principal Investigator: Cristian Guevara (I Physikalisches Institut)
Title: M43 and M17SW [OI] 63 and 145 µm fully sampled maps
Abstract: Our recent observations with SOFIA/upGREAT at very high velocity resolution and S/N of [12CII] and [13CII] lines have shown for a number of sources, M43 and M17 between them, that the [CII] line is optically thick and, for M17, is heavily affected by self-absorption. This is due to absorption of the background emitting layer by a colder foreground layer of [CII] associated with some velocity components of the source. Both, the high column densities of the warm emitting gas, and in particular the nature of the rapid variating colder foreground absorption gas, are very hard to explain in the context of standards PDR models. New [OI] 63 and 145 μm observations at the 7 positions observed in [CII] for M17 SW, have shown that [OI] 63 μm follows the same line profile of the self-absorbed [CII], including its absorption dips, meanwhile [OI] 145 μm shares the same line profile with the optically thin [13CII]. This phenomena motivate us to obtain fully sampled [OI] maps for both transitions for M17 and M43. M17 is one of the brightest and most massive giant molecular clouds in the Galaxy. It is illuminated by a large cluster of OB stars. It is one of the best galactic regions to study PDR structure from the exciting source to ionization source. M43 is a close-by ideal spherical nebula with a single early B type star in the center. Due to its close distance, simple spherical geometry and single ionization source, it is well suited as a simple, properly characterized source. With this proposal, we want to study the distribution of [OI] 63 and 145 μm in M17 SW and M43. We plan to do this through observations of fully sampled maps in [OI] 63 μm and [OI] 145 μm. The main goal is to map the rapid variation in the foreground absorption layer through the comparison of both [OI] lines.
Principal Investigator: Slawa Kabanovic (University of Cologne)
Title: Optically Thick [CII] Emission from Orion A
Abstract: We analyze the [12CII] and [13CII] emission at the interfaces of HII regions (NGC 1977, M43 Veil Bubble, etc. ) and the dense molecular gas in Orion A. Spatial averages over square-arcmin regions from the SOFIA Impact Program. The large scale [CII] emission from the Orion molecular cloud have shown the [12CII] emission to be optically thick and showing foreground self-absorption. The primary goal is to obtain high S/N full spatial resolution maps of [13CII] in order to determine if the high optical depth and foreground absorption features visible in the drastically spatially averaged spectra from the Orion survey are located features or smoothly distributed. In addition, the data will allow to estimate the physical conditions (excitation temperatures, column number densities, etc.) and the kinematicsof the [CII] emission. Using the upGREAT heterodyne array instrument on board SOFIA we will obtain high-S/N maps in the [CII] 158 μm line of selected regions of interest, where the spatial averaged spectra from the Impact Program show evidence for high optical depth and self- absorption. Our recent findings show the presence of high optical depth and foreground absorption in the extended Orion emission. With this proposal we will be able to address the important question whether the optical depth peaks locally toward a few lines-of- sight, or whether it is uniformly distributed. Similarly, the spatial structure of the foreground absorption of unknown origin will give hints towards its possible origin. We will use the data as an input for our two-layer multicomponent model (Guevara et al. 2019). The fit of the radiative transfer equation to the observed [CII] and [13CII] lines will give us information about the physical conditions and the spatial structure of the predicted cold [CII] foreground.
Principal Investigator: Haojing Yan (University of Missouri-Columbia)
Title: HAWC+ Observations of Planck-selected 550 micron Peakers
Abstract: The Planck CMB mission has also provided the first all-sky survey of astrophysical sources in the sub-mm/mm regime. Of particular interest among these sources are those of red sub-mm colors that resemble dusty starbursts at high redshifts. These sources are very bright (> 200 mJy), implying extremely high luminosities (> 10^14 Lsun) if they are indeed at high-z. The natural explanation would then be that they are either galaxy clusters or gravitationally lensed individual galaxies. In either case, these sources are important because they form a complete sample of the most extreme sources in the universe from an all-sky survey. Follow-up studies, however, are hindered by the very coarse spatial resolution of Planck (~ 5'-5.5' at 350--850 micron), and higher resolution imaging at similar wavelengths is necessary to pinpoint the exact source locations. A few programs have been carried for this purpose using the early and the first release of Planck compact sources. Using the Second Planck Catalog of Compact Sources (PCCS2) based on the full Planck mission data, we have selected a sample of five "550 micron peakers" whose SED peaks are at 550 micron. Two of these five objects are in the directions suitable for SOFIA observations, and here we propose HAWC+ total intensity measurements in E, D and C-bands. Our results will facilitate the interpretation of these brightest sub-mm sources in the universe by determing whether they are lensed or clusters and by enabling a full SED analysis. Very importantly, the results will also provide positions accurate enough for future follow-up studies at other wavlengths. We request 8.2 hrs in total.
Principal Investigator: Michael Kaufman (San Jose State University)
Title: An upGREAT Map in M20: [OI] and [CII] Emission from a Young Star Forming Region
Abstract: Using upGREAT to map 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. This is a resubmission of an accepted Cycle 6/7 proposal that has produced beautiful velocity-resolved CII images of the mapped region, including the first CII map of the velocity gradient along the photoevaportaing globule. The [OI] and CO mapping proposed here will alow us to complete the project.
Principal Investigator: Mark Heyer (University of Massachusetts)
Title: Testing models of molecular cloud formation in converging gas streams
Abstract: With the upGREAT instrument, we propose to make sensitive maps of CII 158 micron emission surrounding two molecular clouds to define the spatial and kinematic relationship of the cold, neutral atomic gas and CO-dark gas with respect to the fully molecular gas defined by CO observations. These data will test the predictions of cloud formation theory in which molecular clouds form in the interface regions of converging flows of atomic gas. Specifically, we will search for velocity offsets and gradients of the CII emission with respect to the CO velocity that would indicate the presence of a converging flow. Detecting evidence for such flows and their role in forming molecular clouds would provide a significant advance in our understanding of the neutral ISM and star formation.
Principal Investigator: Takuya Hashimoto (Waseda University)
Title: FIFI-LS Spectroscopy of Two Confirmed Lyman Continuum Emitters
Abstract: Understanging the reionization process is a big quest of modern astronomy. The escape fraction of hydrogen-ionizing photon (LyC) from galaxies into the surrounding intergalactic medium (IGM) is a key factor in reionization. Unfortunately, direct LyC observations for z>6 galaxies are impossible due to virtually zero IGM transmission for LyC. Thus, current efforts are focused upon establishing a link between the LyC escape fraction and other observables in the local Universe. With ALMA, our team has demonstrated that [OIII] 88 micron is brighter than [CII] 158 micron by a factor of 2 to 12 in star-forming galaxies at z>6. Such high line ratios would imply highly ionized interstellar media with a low neutral gas content, facillitating the LyC escape, although we cannot directly observe their LyC. If we could establish a link between the LyC escape and the [OIII]/[CII] ratio in the local Universe, we can interpret ALMA results in terms of the LyC escape. In this study, we aim to investigate a possible link between the [OIII]/[CII] ratio and the LyC escape for the first time. Here we propose to perform FIFI-LS observations of two carefully selected LyC emitters (LCEs), Mrk 54 and Tololo 1247-232, targeting [CII] and [OIII]. Based on a combined sample of three LCEs, one from the literature (Haro11) and two from this study, we intend to investigate if high [OIII]/[CII] ratios are commonly seen in LCEs. It is only with FIFI-LS observations of local LCEs that we can connect the [OIII]/[CII] ratio with the LyC escape physics. Our observations will be also useful to invesitgate if the relation between SFRs and FIR line fluxes apply for LCEs. The proposal is a resubmission of an approved but not completed Cycle-7 project.
Principal Investigator: Alberto Bolatto (University of Maryland)
Title: Studying the Energetics of Galaxies with Velocity-Resolved [CII] Observations in an IFU-Selected Galaxy Sample
Abstract: The regulation of star formation in galaxies is one of the open problems in galaxy evolution. Large spectroscopic samples of spatially-resolved galaxies observed with Integral Field Units and interferometers are revolutionizing our understanding of the inner workings of galaxies, providing key information about the stellar populations, and the ionized, atomic, and molecular gas. Missing from this picture is the key information of gas cooling and energetics provided by far-infrared [CII] observations. We propose a velocity-resolved survey of [CII] in a Integral Field Unit-selected sample of nearby galaxies with excellent CO interferometric observations, close enough to be spatially-resolved to SOFIA. These observations take advantage of the upGREAT 14 pixel receiver. The ability to resolve the kinematics of the [CII] emission allows us to use spectral decomposition techniques to disentangle the contribution of the molecular and atomic phases. We will use these observations to study the ISM thermal pressure in disks in relation to the abundance of star-forming gas, the use of [CII] emission to trace total gas mass, and the efficiency of star-formation at heating the gas. The proposers are an experienced team of extragalactic experts who have led some of the key surveys of nearby galaxies. We are committed to publicly release the survey data as part of the EDGE and PHANGS efforts in easy-to-use format, to increase the community access to SOFIA data and impact of the observations.
Principal Investigator: Archana Soam (SOFIA Science center/USRA)
Title: Do I sit in the sun or in the shade? An EXES proposal to observe H2 pure rotational excitation in IC 63
Abstract: We propose to use the EXES high-medium long (24") slit mode to observe H_2 v=0 J=3-1 and J=7-5 across the most intense H_2 emission ridge in the reflection nebula/Photodissociation Region (PDR) IC63. We will measure the gas temperature along the long EXES slit, to quantify the temperature dependent gas-grain collision rate in gas directly exposed to the light from gamma Cas, and gas in the shade of one or the dense molecular clumps. This will extend and clarify the results from Thi et al. (2009) who used low spatial resolution ISO-SWS observations to show a two-temperature gas distribution in the region. Because the large area of their aperture, the spatial dependence of the temperature is, however, not clear. We aim to directly test the hypothesis that the gas temperature is different "in the sun and in the shade" by spatially resolving the H_2 excitation into the shaded and the "full illumination" areas in IC 63. We will combine these observations with our existing high-resolution HCO+, CO, [C II] and H I observations to analyze the PDR physics. While the lines (only) available to EXES are critical for determining the excitation structure, we will complement these data with observations of the J=2-0 line with SOFIA/HIRMES, once available and J=6-4 with IRTF/TEXES (proposal pending). Combining EXES, HIRMES and TEXES observations will allow us to fully evaluate the spatial dependence of the H2 excitation temperature on FUV illumination and better constrain the gas and dust dynamics in the PDR.
Principal Investigator: Howard Smith (Center for Astrophysics | Harvard and Smithsonian)
Title: Measuring the Peak Far IR Dust Emission Profiles in Luminous Galaxies
Abstract: Radiation from warm dust dominates the emission of infrared luminous galaxies, and together with radiation from stellar photospheres, evolved stars, and other processes, comprises a galaxy’s spectral energy distribution (SED). The dust is primarily heated by star formation (SF) and active nuclei (AGN) activity, and SED analyses can recover the information about these and other contributing processes. We have remeasured the UV-FIR (GALEX-to-SPIRE) photometric SEDs of 190 luminous, star forming galaxies and successfully modeled them using the CIGALE fitting code to derive most probable key galaxy parameters, from SF and AGN activity to the dust and stellar masses. Unfortunately, more detailed understanding of the physical conditions of the emitting dust, however, has generally not been possible because nearly all analyses to date rely on just a few photometric datapoints that sparsely sample the dust peak (from about 50-200μm) with only one or two IRAS points and sometimes PACS photometry. Typically only a few simple parameters can be derived, like the Dale & Helou alpha parameter (Dale et al, 2002,2014) which only approximately reflects the true ranges of dust temperatures that contribute to the emission. A key issue is that measurements of the detailed shapes of dust peaks have been lacking and the information coded in those shapes is unavailable. We propose FIFI-LS spectrophotometry to measure more detailed shapes of the dust emission peak at 17 continuum wavelengths across nearly 2 octaves from ~50 to 200μm (with wavelenths chosen for best atmospheric transmission). We have assembled a set of 32 relatively nearby luminous galaxies (L>10^11L_sol) with F(IRAS100) >10Jy characterized by having no data at the FIR peak except one IRAS point, or little data (a few PACS points). These flux densities are readily detected by FIFI. We propose using CIGALE/THEMIS dust model, DUSTY, and other methods to characterize the dust peaks. The dataset itself will provide the first systematic, detailed look at this prominent and critical feature of luminous galaxies, and will be useful in refining our understanding of the ISM (e.g., [CII] emission), the Schmidt-Kennicutt (S-K) and galaxy Main-Sequence (MS) relations. The diverse set of FIR peaks have never before been systematically measured, and in addition to strongly constraining the model fits, the data will offer a first look at the detailed shapes.
Principal Investigator: Tucker Jones (University of California; Davis)
Title: Accurate chemical abundance measurements: from z=0 to the reionization epoch
Abstract: The gas-phase metallicity of galaxies encodes information about current and past gas inflows, outflows, and star formation. Accordingly, obtaining accurate metallicity measurements for large samples of galaxies is a major goal of galaxy formation and evolution studies. However, current results suffer from large systematic uncertainty in the absolute metallicity scale, revealed by disagreement between different direct measurement techniques. This disagreement can plausibly be explained by fluctuations in the gas temperature within HII regions, but an independent test is needed to determine whether this is indeed the case. We propose to use the unique capabilities of FIFI-LS onboard SOFIA to obtain measurements of the [OIII] 52 µm emission line for a sample of six carefully-selected local HII regions with high-quality optical spectra. The addition of [OIII] 52 µm data will provide an independent determination of the magnitude of temperature fluctuations and the absolute metallicity scale. The results will have an immediate benefit of eliminating the dominant systematic uncertainty in metallicity measurements of >100,000 galaxies at z=0 and >1,000 at z>1. Furthermore, these measurements will provide the framework necessary to combine ALMA measurements of far-IR lines with JWST rest-optical spectra to determine accurate metallicities at z>6 in the epoch of reionization. We will simultaneously observe the [CII] 158 µm line to aid in understanding anomalous far-IR [CII]/[OIII] ratios found for z>6 galaxies using ALMA.
Principal Investigator: Raghvendra Sahai (Jet Propulsion Laboratory)
Title: Shocked and Scorched: A GREAT Investigation of [CII] and [OI] emission from free-floating Evaporating Gas Globules in the W5 Massive Star Formation Region
Abstract: We propose to use GREAT in order to observe [CII]158 micron and [OI]63 micron emission towards 3 select members of a new class of tadpole-shaped free-floating evaporating gas globules (frEGGs) in the W5 massive star-formation region (MSFR). Since discovering the most prominent member of this class in an HST imaging survey, we have now identified substantial populations of such objects in several MSFRs using Spitzer IRAC 8 micron images. By virtue of their distinct, isolated morphologies, frEGGs are ideal astrophysical laboratories for probing star formation in irradiated environments. Our molecular-line observations reveal the presence of dense molecular cores associated with these objects, with masses exceeding 0.5-5 Msun, and our radio continuum imaging reveals bright photo-ionized peripheries around these objects. The ratio of the mass in the photodissociation region (PDR) surrounding the molecular gas can help constrain the evolution of the frEGGs and the total time available for accretion by the star or stars that may form inside it, and their mass function. The line profiles will be used to probe the photoevaporative flow that is expected to drive frEGG evolution. We will use sophisticated 3-D numerical simulations of dynamical and chemical evolution of frEGGS to reproduce our SOFIA data and additional existing multiwavelength data on frEGGs. The proposed study will allow us to probe the effects of a less energetic external environment on star-formation in irradiated molecular cores by comparison with our Cycle 5 pilot study of 3 frEGGs in the Cygnus MSFR. We discovered photo-evaporative outflows and found the mass of atomic gas to be a small fraction of the total mass budget in these frEGGs, implying that they are relatively young. This study will pave the way for a larger SOFIA survey of frEGGs, leading to new insights into the complex star formation process in UV-irradiated environments.
Principal Investigator: Archana Soam (SOFIA Science Center)
Title: On the [CII] kinematics of a bright-rimmed cloud undergoing radiatively driven implosion and triggered star-formation
Abstract: The interaction of newly formed stars with their natal clouds give rise to a number of dynamical and chemical effects, forming H II regions, injecting energy in the surrounding ISM and, potentially giving rise to triggered star formation. When an expanding H II region encounters density enhancements, Bright Rimmed Clouds (BRC) are formed, containing photo-dissociation regions (PDR). These provide valuable laboratories of radiation driven dynamics and physical/chemical evolution of the gas and dust. We propose to map a nebula BRC 18, in the [C II] line, a well-known PDR tracer, with the SOFIA/upGREAT. These observations will complement a significant amount of existing ancillary data tracing the molecular gas and dust in the cloud at different spatial scales. This cloud is situated in HII region Sh2 -264 at a distance of ~390 pc and illuminated by an O8 type star λ−Ori. The [CII] observations from SOFIA/GREAT in an evolved BRC IC1396A nebula have already been acquired and publised. A combination of existing [CII] data in IC1396A and proposed observations will provide a unique environment to investigate the kinematics of PDRs at different evolutionary stages. Because of the high spectral resolution of upGREAT, our observations will provide detailed information about gas flows and turbulent motions, providing important constraints and test for models of radiation driven cloud evolution and the chemistry and physics of PDRs. The orientation of [CII] gas motion gradients will also be compared with the existing densely sampled magnetic field topology of the cloud.
Principal Investigator: Urs Graf (University of Cologne)
Title: Disentangling the line-of-sight structure of NGC 2024
Abstract: Proposal 07_0132 has been awarded 5.8 hours of observing time on SOFIA in Cycle 7 under the rating "Should Do". We resubmit the proposal as a contingency for Cycle 8 if the observations cannot be completed in Cycle 7. We propose to map the central region of NGC2024 in [13CII]. Due to the strong foreground obscuration of the source, the standard fine-structure line tracers of the warmest PDR gas ([12CII], [OI] at 63 and 145 microns) are all heavily self-absorbed. Up to 85% of the intrinsic source emission can be hidden by the foreground (estimate for [OI] at 63 microns). Only [13CII] will give us a clear view of the main source, and, for the first time will enable us to study in detail the physics of this gas component over the whole area. With upGREAT we now have the means to integrate deep enough in a large enough region to cover the main emission area as seen in an earlier [OI] 145 micron map. The very high signal to noise [12CII] map that automatically comes with this observation, will give valuable information on the spatial and spectral distribution of the foreground material, and will also allow to estimate the emission contributed by the hot gas in the [HII] region. The second frequency band of upGREAT will measure a high quality map of the heavily self-absorbed 63 micron [OI] line. This will improve our knowledge of the foreground gas component, because with the higher absorption coefficient and the higher spatial resolution of this transition, we are more sensitive to small areas of weak absorption.
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 3.5 hours of total observing time to complete the proposed task. This is a re-submission of proposal no. 06-0146, which had been awarded 3.78 hours of observing time in CategoryII. However, the proposal has not yet been scheduled and therefore is resubmitted with slight modifications and an updated (slightly reduced) time estimate.
Principal Investigator: Jens Kauffmann (Haystack Observatory; Massachusetts Institute of Technology)
Title: Tracing cosmic star-forming Gas: Connecting Cii, HCN, and other Species in the LEGO Survey
Abstract: We wish to examine whether the millimeter–wave emission of HCN correlates with the emission of [CII] as probed by SOFIA. We will do so by mapping [CII] in a representative sample of molecular clouds for which we have obtained HCN data as part of our LEGO Large Program on the IRAM 30m–telescope. This experiment is of fundamental importance for progress in extragalactic star formation research, as it is needed to reliably interpret the so–called Gao & Solomon relation. Specifically, this project examines whether HCN can serve as a reliable tracer of dense gas (i.e., densities >10^4 cm^–3) in other galaxies, or whether the excitation of HCN is to a significant extent influenced by the electrons released during the formation of [CII]. Excitation by electrons would enable bright HCN emission in gas of low density, fundamentally changing the interpretation of HCN emission as a central tool for the study of galaxies. The LEGO sample is unique in that it uses a significant allocation of observing time (i.e., about 600 h) to systematically explore molecular line emission between 85 and 115 GHz in a sample of molecular clouds that is representative of the Milky Way, i.e., ranging from the inner Galaxy to the outer disk. This provides us with unprecedented wide–field views of many critical molecular species, such as HCN, CS, and N2H+. We have now used this sample to systematically identify a subset of molecular clouds with remarkable trends in HCN emission. We now wish to obtain [CII] maps, as such data are critical for the interpretation of our existing data. A secondary goal is to use the new [CII] maps — which will be among the largest and most sensitive maps taken so far — to better explore the nature of [CII] emission in molecular clouds. Specifically, we can examine how [CII] emission depends on the physical conditions revealed by the 10–15 emission lines imaged by the LEGO survey. This aids future work with SOFIA on [CII] emission by any investigator.
Principal Investigator: Alison Coil (University of California San Diego)
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 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 identify or rule out contributions from obscured AGNs. Building on successful SOFIA observations of one of our sources in Cycle 6, here we propose to use HAWC+ in total intensity mode with the C and E filters to target a second galaxy and use the combined data from both cycles to measure the SEDs of two galaxies from 60-140 µm in the restframe (90-215 µm observed). We will combine the HAWC+ data with our existing 0.1-14 µm observations to measure the bolometric output of these systems, decompose their star formation and AGN activity, and test whether the winds can be driven by star formation alone or whether an AGN feedback component is required. These galaxies are excellent lower redshift analogs of the z > 3 progenitors of today's massive early-type galaxies and provide us with an unprecedented opportunity to study star formation and feedback at its most extreme. Notably, no other objects of this nature have existing measurements in the far-IR, such that our observations with HAWC+ are enabling entirely new science and highlighting the extragalactic potential of SOFIA.
Principal Investigator: Jingzhe Ma (University of California; Irvine)
Title: Are local ULIRGs low in metals? Testing a new metallicity diagnostic with FIFI-LS.
Abstract: A comprehensive study of the physical properties of low-z ultra luminous infrared galaxies (ULIRGs), specifically their interstellar medium (ISM), is critical to understanding the evolution of >L* galaxies and active galactic nuclei across cosmic time. ULIRGs at low redshifts are central to this endeavor, as they establish a baseline from which to measure evolution with redshift in the ULIRG population. We propose FIFI-LS observations of the far-IR (FIR) fine structure lines of 11 ULIRGs selected by IRAS at 0.01 < z < 0.13, primarily targeting the [OIII]52 and [NIII]57 µm lines, which are currently only accessible by FIFI-LS. The proposed observations will provide comprehensive diagnostics of the physical conditions of the ISM such as the gas density, radiation field intensity, and metallicity that is much less susceptible to extinction than traditionally used UV/optical transitions. We will be able to apply the excellent FIR metallicity diagnostic, ([OIII]52+2.2[OIII]88)/[NIII]57, for the first time, which breaks the density degeneracy and reduces the scatter in the correlation to within 0.2 dex. The unprecedentedly reliable metallicity measurements will address whether ULIRGs lie below the mass-metallicity relation of star-forming galaxies as previously thought based on optical metallicity diagnostics. Along with archival Herschel/PACS+SPIRE observations, we will be able to test all the line-ratio diagnostics by comparing to models (e.g. Cloudy) and identify the best pairs to optimize future observations with ALMA for high-z analogs. This pilot SOFIA program will open up the opportunity to increasing the sample of low-redshift (0.1 < z < 0.3) ULIRGs with the full set of FIR line observations by a factor of 2-3. This program will also demonstrate a key science program for the Origins Space Telescope that focusses on metallicity measurements out to z of 6 with results from Cycle 8 potentially making an impact in Astro2020 Discussions.
Principal Investigator: Seamus Clarke (I. Physikalisches Institut; University of Cologne)
Title: [CII] as a tracer of pre-shock and post-shock gas in a supernova remnant
Abstract: Fast supernova remnant (SNR) shocks emit high energy photons, and cosmic rays, which are absorbed by the pre-shock gas, altering its chemical and thermal properties. When the shock impacts regions of the dense ISM, the shocked gas is able to cool rapidly to produce a hot dense post-shock region, bright in atomic and ionic fine structure lines. We aim to observe the [CII] 157.7 micron line to probe the pre- and post-shock gas in parts of the X-ray luminous CTB 109 (G109.1-1.0). CTB 109 is associated with a giant molecular cloud (GMC) complex, making it a prime choice for studying the interaction of a SNR with dense ISM gas. With the large bandwidth and high velocity resolution of the upGREAT receiver we will be able to capture and resolve both the pre- and post-shock [CII] components. Combined with previous observations of CO, dust, X-rays and radio, the [CII] emission will allow us to probe the pre-shock gas, the shock layer, and the post-shock gas, giving an unprecedented picture of the gas covering the molecular, atomic and ionised phases of the ISM. A new radiative shock model being developed in Cologne which includes hydrodynamics, non-equilibrium chemistry, radiative transfer of UV and X-ray photons and non-equilibrium ionisation populations will allow us to self-consistently model the pre-shock and post-shock regimes and determine important shock properties such as its velocity, initial energy, age and the pre-shock density. We ask for 3.5 hours of total observing time to complete our mapping region.
Principal Investigator: Nicholas Ballering (University of Virginia)
Title: Probing Protoplanetary Disk Dispersal with the 63 micron Oxygen Line
Abstract: The unique disk around HD 141569 is the midst of transitioning from a primordial protoplanetary disk to a debris disk. The 63 micron [OI] emission line was detected from this system with Herschel/PACS, but it was not spectrally resolved, so we have no constraints on where it originates. We will locate the source of this line by resolving its spectral profile with SOFIA/GREAT. In doing so we can ascertain whether the line originates from a photoevaporative wind or from the gaseous disk. The detection of a wind would provide evidence that photoevaporation likely plays a role in the final stages of disk dispersal. The 63 micron line is sensitive to cooler gas than typical wind tracers at optical wavelengths, so the line profile will provide new kinematic constraints on the wind-driving mechanism. If the line originates from the disk, we will fit its Keplerian profile to determine its location. Comparing this with the known location of molecular CO will reveal where the gas disk is photodissociating, while comparisons with the known features in the dust disk can highlight the role that radiation pressure plays in shaping this disk. Finally, our results will help to refine physical models of the disk to better understand the role that [OI], a powerful interstellar coolant, plays in setting the disk temperature.
Principal Investigator: Jean Turner (UCLA Department of Physics and Astronomy)
Title: CO from Hot Molecular Cores in a Forming SSC
Abstract: Super star clusters (SSCs), the likely progenitors to globular clusters, are unusual star-forming environments. The prototype of an SSC cloud is the source in the local dwarf galaxy, NGC 5253. ALMA observations show that the gas in this SSC cloud is very hot, so hot that low J CO lines cannot constrain the gas temperature, density, pressure, or masses. We propose that the CO emission in this cloud represents conditions in X-ray-irradiated clouds, XDRs, rather than PDRs, with the hard radiation field coming from very massive stars within the cluster. We propose to observe CO(16-15) to allow modeling of the CO lines, which will allow us to measure CO mass and characterize other cloud properties.
Principal Investigator: Oriel Humes (Northern Arizona University)
Mid-Infrared Spectroscopy of Primitive Asteroids in the Middle Solar System
Abstract: Asteroids in the middle solar system--the Jupiter Trojans, Hildas, Cybeles, and Main Belt asteroids--have been used to constrain the dynamical history and evolution of the solar system. By observing the 10 and 20 micron silicate features, we seek to understand inter-group relationships between these populations and their implications for early solar system history. This region of the mid-infrared is particularly useful as it contains silicate emission features known to be present on the Trojan asteroids as well as spectral signatures of the hydration state of surface silicates. We propose observations of a collection of D & P type asteroids in the Hilda, Cybele, and Main Belt groups using the FORCAST G111 and G227 grisms on SOFIA. These observations will enable the comparison of the mid-infrared spectra of primitive objects in the Hilda, Cybele, and Main Belt to existing observations of Trojan asteroids in the literature. A shared spectral signature among these groups would point to a shared common origin of primitive asteroids in these populations. In addition, analysis of the hydration states of these asteroids will provide constraints on the timing and location of these objects during the formation of the solar system. The end result of these observations will be a catalog of mid-infrared spectra for a collection of primitive asteroids and the comparison of these spectra to existing observations of the Trojans to yield a better understanding of their shared formation histories.
Principal Investigator: Ryan Arneson (SOFIA Science Center)
Title: Dust Mineralogy of Proto-planetary Nebulae: RV Tauri Stars and SRd Variables
Abstract: We propose to obtain SOFIA/FORCAST grism spectra to examine the mineralogy of the circumstellar dust in a sample of post asymptotic giant branch supergiants that are believed to be the precursors of proto-planetary nebulae. We are proposing here to finish observing the remaining stars from our Cycle 3 program during Cycle 8 and to extend the sample to contain the rest of the brightest RV Tauri and SRd stars, including those in the southern hemisphere. The proposed program will produce the first self-consistent sampling of the entire 4.9-37.1 micron spectral region for a broad cross-section of this class of objects. The wavelength coverage and spectral resolution of the grisms will allow us to produce accurate models of the composition and grain-size distribution of the dust and to test for the presence of a dual-chemistry composition of the circumstellar material. Relationships between the chemical composition of the circumstellar dust and the elemental abundances of the central stars will be investigated. Models of the distribution of dust in the circumstellar environments of these stars can also be constrained by the data. Eight of our thirteen program stars are all accessible to SOFIA flights that occur from Palmdale, CA during Cycle 8. The remaining five stars require a southern deployment.
Principal Investigator: Caitlin Casey (University of Texas at Austin)
Title: Precision Cosmology with SOFIA: Characterizing the Dust Emission in Nearby Supernovae Type Ia Host Galaxies
Abstract: We propose to directly measure the dust in SN Ia host galaxies to better understand how host galaxy ISM physics may impact precision supernovae cosmology. The physics of the ISM in and around Type Ia supernovae (SNe) is soon to become the dominant source of uncertainty as cosmological surveys enter an era of large statistical samples, with the Dark Energy Survey and LSST. Historically, SN cosmology has predominantly assumed a uniform reddening law to correct for dust extinction along the line of sight, both for dust in the Milky Way and in the host galaxy of the SNe. It has become apparent that there is a trend between host galaxy stellar mass and Hubble residuals (the residuals on the distance modulus) of unknown origin, and that dust in the host galaxies might be the root cause of this correlation. If so, it is likely that an even stronger correlation between SN color and host galaxy dust mass, or Hubble residuals and dust mass, exists. Furthermore, there is tension between the measurement of the Hubble constant from local Cepheid calibrators (of which there are a total of 19 galaxies with both Cepheid and SNe Ia distance indicators), and Type Ia hosts embedded in the Hubble flow, which could be caused by host galaxy dust characteristics. We select a diverse range of 18 galaxies within D<100Mpc for resolved spatial observations of dust emission with SOFIA HAWC+ to directly infer correlation between line-of-sight dust mass towards the galaxies' SNe with residual measurements on their distances to inform future large SNe campaigns. Five of the 18 targets are also Cepheid calibrators, enabling a more detailed study of line-of-sight attenuation toward both Cepheid and SNe Ia distance indicators. This is a resubmission of a cycle 7 program, for which five of 18 targets were observed (none of which are Cepheid Calibrators; 8 more are scheduled but not yet observed). We are seeking completion of the program in Cycle 8.
Principal Investigator: William Vacca (USRA)
Title: Tracing the Atomic Gas Component of the Galactic Wind in the Prototypical Starburst Galaxy He 2-10
Abstract: Mass outflow, in the form of a galactic wind, has been recognized to be a fairly common phenomenon among starburst galaxies. Powered by the radiation and mechanical energy and momentum of the massive stars formed during the starburst and their subsequent supernovae, galactic winds transport material out of the galaxies and into the intergalactic medium, enhancing its dust content and metallicity. These winds also play a pivotal role in the evolution of their host galaxies: by driving material out of a galaxy, they regulate star formation (feedback) and can affect the chemical evolution of low mass galaxies. We are requesting time to obtain deep observations using SOFIA/FIFI-LS of four fields in the outskirts of He 2-10, where Halpha images reveal the presence of gas outflow, in the form of a galactic wind. We propose to image these fields in the lines of [O III] 52 and 88, [O I] 145, and [C II] 158 microns, all of which trace the cool atomic gas component. We will compare these observations with the H alpha images (which trace the hot, shocked gas) to determine the relative spatial distributions of the cool and hot gas components, and therefore the determine if the cooler gas component is coupled to the hot gas. The [O III] line ratio provides an estimate of the electron density. We will combine the proposed observations with previously obtained FIFI-LS GTO data to generate a spatial map of the density and trace its value from the central starburst into the galactic wind. The combination of the [O I], [O III], and [C II] data will allow us to carry out a PDR analysis of the material in the wind and determine the gas properties. This will then provide insights to the nature and structure of the galactic wind, including the total energy and mass involved and the source of the ionization (shocks vs photoionization). We will then compare the properties of the galactic wind in He 2-10 with those of the wind in M82. Finally, we will use the [C II] map to search for the atomic gas component corresponding to the CO tail previously detected in this object.
Principal Investigator: Ryan Lau (ISAS/JAXA)
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. Imaging 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.
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). Recent 15 mu-arcsec angular resolution images using the ground-based adaptive optics system SPHERE (Schmid et al. 2017) have revealed a bright H-alpha source related to the source of the jet and resolve the R Aqr binary. Bujarrabal et al. (2018) used ALMA to directly image the gravitational effects of the secondary on the stellar wind. These exciting new discoveries compliment the to be discovered changes in this fascinating symbiotic system. We propose to obtain grism spectra across the silicate features, and photometry at several wavebands between 5 and 37 mu-m at two different Mira phases using FORCAST, and longer wavelength photometry in four bands between 58 and 214 mu-m 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.
Principal Investigator: James Jackson (SOFIA Science Center)
Title: AGAL313.576+0.324: a Luminous Clump with a Remarkably Low [C II]/FIR Luminosity Ratio
Abstract: Although [C II] emission from galaxies is now widely used to indicate the global star-formation rate, it is important to refine our understanding by calibrating the local relationship between [C II] emission and starformation. Our recent study attempts to test the idea that extragalactic [C II] emission can arise from a collection of high-mass clumps like those found in the Milky Way. We find that three of the four clumps we have studied match the empirical extragalactic [C II]/FIR luminosity ratios appropriate for their dust temperature, but one source, AGAL313.576+0.324 ("G313"), is under-luminous in [C II] by a factor of at least 100. Although G313 has a substantial FIR luminosity (24,000 LO) indicating ongoing star formation, no significant [C II] line emission was detected with FIFI-LS. We will use GREAT to test two possibilities: (1) AGAL313.576+0.324 is a protostar with no UV flux, and thus [C II] emission is actually absent, or (2) [C II] emission is present but it is canceled by deep absorption features in the coarse FIFI spectral resolution element. With only 35 minutes of telescope time, we can make a small 2'' x 2'' map with sufficient sensitivity and spectral resolution to confirm or refute both hypotheses. If such clumps are common, it will be important to include these "[C II] dark" clumps in any attempt to model extragalactic [C II] emission.
Principal Investigator: Paul Lucey (Hawaii Institute of Geophysics and Planetology)
Title: Water abundance on the Moon from 6 micron observations
Abstract: Spacecraft observations of the Moon showed a hydrogen-bearing species caused an unexpected 3 μm absorption. However, existing data at 3 μm cannot resolve the chemical form of this hydrogen, whether molecular water (H2O) or the hydroxyl radical (OH-) attached to a metal cation. The chemical form of the 3 μm absorber provides information on solar wind interaction with the lunar surface, and whether the hydrogen- bearing compound is mobile and can form and sustain known ice deposits at the lunar poles. Low resolution spectroscopy at 6 μm is uniquely sensitive to the presence of molecular water in a spectral region both inaccessible from the ground and lacking in existing and planned spacecraft observations. The project will produce 6 μm spectra of the Moon as a function of local time, location and temperature for use by the wider planetary astronomy and lunar science community.
Principal Investigator: Jochen Eisoffel (Thüringer Landessternwarte)
Title: Catching the next bright accretion burst from a YSO on the rise
Abstract: Low-mass stars form via circumstellar disks through which matter is accreted onto the protostar. In recent years, it has become clear that this process is episodic and highly variable and -- occasionally -- leads to strong accretion bursts (so-called EXor or FUor outbursts), which are likely caused by inward migration and absorption of dense eddies. The recently (by our team) discovered accretion burst in the high-mass young stellar object S255IR NIRS3 (HMYSO; M > 8 M_sun, L_bol > 5x10^3 L_sun) and the almost contemporaneous one associated with NGC6334I-MM1 indicate that HMYSOs experience disk accretion as well, and identify disk-accretion as the primary mechanism of star formation across the entire stellar mass spectrum. Of utmost interest for our understanding of this process and its consequences is now to find out which parts of the disk are affected by the outburst and on which timescales, and how this may vary with mass of the protostar. Here we are requesting Target-of-Opportunity observations for the next bright accretion burst in a YSO with FORCAST and FIFI-LS/HAWC+ observations (1h/45min each) while the outburst is on its rise, and a follow-up a few months later to follow the heatwave moving through the accretion disk. With these data we will derive the spectral energy distributions of the source. This constitutes an excellent dataset to learn more about where in the circumstellar disk such a burst starts, how it is triggered, and what its implications for planet formation may be.
Principal Investigator: Alexander Tielens (University of Maryland)
Title: EXES Survey of the Molecular Inventory of Hot Cores
Abstract: The formation of massive stars is a complex interplay of a number of processes including accretion, disk formation, heating, outflow activity, and ionization & expansion. Each of these processes has a clear kinematic signature and, leaves a chemical imprint on the organic inventory of the source components present. However, processes at the smallest scales are difficult to observe at sub-mm wavelengths because of beam dilution combined with a swamping of the signal by bright emission from a warm environment. High spectral resolution, pencil beam absorption line studies at mid-IR wavelengths provide a unique diagnostic of these small-scale regions as the absorption originates in the densest gas close in the inner regions where e.g., jets & winds interact with disks as they are accelerated outwards. We propose to use EXES on SOFIA for a complete, high signal-to-noise (S/N~100) and high spectral resolution (R=50,000) survey of the 5.4–8 μm region of the Hot Core associated with the massive protostar W3 IRS 5. This survey will be complemented by surveys in the M and N bands from the ground at comparable spectral resolution. One main goal of MIRI/JWST focuses on understanding the evolution and chemical composition of low mass star forming regions through mid-IR observations and many of the physical (e.g., outflows, disk-wind interaction) and chemical (e.g., evaporation, energetic processing by shocks and X- ray/FUV radiation) processes involved are very similar to those in Hot Cores. However, JWST/MIRI lacks the spectral resolution to separate individual dynamical components. The proposed SOFIA observations will be instrumental in guiding these studies by identifying specific tracers for the dynamical components and processes relevant to these environments. These lines can be analyzed using simple rotational diagrams to derive the physical conditions for the different kinematic components detected.
Principal Investigator: Peter Weilbacher (Leibniz-Institut für Astrophysik Potsdam (AIP))
Title: Mapping the FIR line emission of the Antennae Galaxy (NGC 4038/39)
Abstract: We intend to map the Antennae Galaxy (NGC 4038/39) in the [CII]158µm and [OIII]52µm emission lines. At sites of high infrared continuum emission signifying high star-formation rates and around active galactic nuclei (AGN), [CII] line emission has been known to be suppressed. Our primary aim with this dataset is the study of this [CII]-deficit over the prototype merger. Since it shows regions of different star-formation intensities but does not contain AGN, the Antennae Galaxy is the ideal target to check the spatial distribution of the [CII]-to-continuum ratio using FIFI-LS spectra in conjunction with existing data from Spitzer and Herschel. Using the same dataset we will be able to check the possible [CII] detection at the location of a compact molecular cloud, that was classified to be a massive globular cluster about to start forming stars. Should the detection of line emission be confirmed, this would suggest that stars have already formed in this object. Finally, using the [OIII]-to-[CII] ratio from SOFIA and our existing VLT/MUSE data we will be able to check suggestions that this line ratio can be used to detect star-forming objects that leak significant amounts of Lyman-continuum emission. This will have implications for local Lyman-continuum emitters and starburst galaxies at high redshift.
Principal Investigator: Antoine Gusdorf (LPENS, École Normale Supérieure, Paris Observatory)
Title: The far-infrared view of the Cepheus E protostellar outflow
Abstract: Protostellar jets and outflows play a critical role in the evolution of the interstellar medium (ISM) of galaxies, in which they input energy in all possible forms: mechanical through the shock waves they drive, far-UV photons from the protostar or from the fastest shocks, and cosmic rays (CRs) that can be locally accelerated. Mapping the Cepheus E outflow from an intermediate-mass protostar in the far-infrared (FIR) range will allow us to understand the physical processes associated to the outflow structures, as well as their energetic and chemical impacts. It will also allow us to probe the formation process of thestar and its outflow. Finally it will provide constraints to study the possible acceleration of particles in its energetic shocks. We request to map the entire outflow in the [OI] 3P1-3P2 and [CII] 2P3/2-2P1/2 lines. Combined with observations acquired by our team (from SOFIA, the IRAM-30m, the PdBI, JCMT, and Herschel telescopes), they 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) from the maps. Then, the Paris-Durham shock model will be applied to better understand shock physics and chemistry. At this stage, we will compare the outflows characteristics to models of outflows formation. Finally, a dedicated model of particle acceleration will be used to assess the potential of this outflow to generate cosmic rays. A map of an entire protostellar outflow in [OI] 3P1-3P2 and at 6'' resolution will be an unprecedented showcase of SOFIA's capabilities. Together with the [CII] 2P3/2-2P1/2 map, it will also bear valuable scientific information. In the future, we will draft proposals to observe the outflow with JWST, in particular in H2 lines that provide excellent and complementary diagnostics to the physical conditions in shocked regions.
Principal Investigator: Jeroen Bouwman (MPIA Heidelberg)
The nature of crystalline silicates in the protoplanetary disk of AB Aurigae
Abstract: We propose to observe the circumstellar disk in the Herbig Ae/Be system AB Aurigae with the FIFI-LS spectrograph. Specifically, we want to target the 69 micron region, where a spectral feature of the crystalline variety of the iron-magnesium silicate Olivine leaves its mark. The derived shape, width and exact wavelength centroid of this spectral feature can be exploited to infer the temperature during the grain formation as well as to constrain the ratio of iron to magnesium in these silicate grains. This in turn gives decisive insights into the thermal and chemical conditions when these grains formed. For our target, Herschel/PACS observations had indicated the existence of the 69 micron emission feature for that disk, but those observations achieved just a relatively low signal-to-noise ratio, and the ambiguous feature fit placed this object in a peculiar part of the parameter space. Such spectral dust features are much broader than common gas spectral lines, and hence a moderate spectral resolution is sufficient to do such a measurement. The FIFI-LS instrument is thus perfectly suited to attempt such an observation for which we will employ a spectral scan with a wide sweep of 3 micron to cover the feature. No other active facility is currently able to do such a measurement. It will settle the question whether AB Aurigae is indeed a special disk in terms of its dust properties. And it can be a pathfinder to further such observations with FIFI-LS, and in the future, potentially, also with HIRMES.
Principal Investigator: Virginie Faramaz (JPL-Caltech)
Title: Where does the dust in the Habitable Zone of Beta Leo come from?
Abstract: The nearby star beta Leo hosts a debris disk with dust extending over a wide range of separations, from ~70 AU down to the sublimation radius. However, the warm dust emission between 30 AU and the habitable zone (HZ) has never been adequately resolved. Consequently, there are serious degeneracies in our models of the architecture, origin, and evolution of this debris disk and the HZ dust. Is the warm dust distributed continuously, or are there gaps in its radial distribution? In the former case, the absence of large grains would indicate that the dust is dragged inward from the outer disk, while their presence would indicate local dust production. The presence of gaps would likely point toward the presence of planets and the wide range of radii at which dust exists in this system makes disk structures due to planet-disk-interaction likely. Spatially resolved multi-wavelength observations with SOFIA tracing multiple grain sizes will permit us to spatially map the dust grain size in the disk and thus to obtain a sufficiently detailed picture of this disk to aleviate our modeling degeneracies. The star's proximity and high luminosity (thus large HZ) make beta Leo one of the very few systems for which detailed constraints on the distribution of dust and presence of sub-Jupiter mass giant planets can be constrained over a wide range of separations from Kuiper belt size down to the HZ with current and near future instrumentation. Our SOFIA data will enable us to do the first, critical step toward this detailed study and will enable and critically complement JWST observations in the near future that will complete our picture of the system.
Principal Investigator: Ralph Shuping (Space Science Inst.)
Title: Short- and long-term variability in pre-transtional disks around high-mass pre-main sequence stars
Abstract: We propose multi-epoch mid-infrared follow-up observations of 3 known pre-transitional disks around young high-mass stars (HAeBe and Be type) observed in OC5 and OC7 (PI: Shuping). Transitional and pre-transitional disks are thought to represent stages in disk evolution from optically thick evolved disks to optically thin debris disks, during which central holes and gaps are created, possibly due to the planet formation process. The mid-infrared ``see-saw'' variability in pre-transitional disks is thought to be caused by vertical perturbations in the inner-disk, possibly due to the interaction between an unseen planetary companion and the inner disk wall. However, this model has only been tested/confirmed for low-mass young stellar objects (YSOs). Our aim is to further test this model by observing higher-mass pre-main sequence objects with known pre-transitional disks to look for variability on week to month-long timescales. If the vertical perturbation model is correct, then we expect to see the "see-saw" variability shift from weekly to monthly (or longer) timescales, due to the increased physical size of the circumstellar disk for high-mass stars. If the "see-saw" variability is observed on weekly timescales, then the model may need to be revisited and additional explanations explored. If the observed variability is different---or absent---this would indicate that the dynamics and energetics associated with pre-transitional disks around hot stars is quite different than for their low-mass cousins, despite the fact that they share very similar architectures. We will also compare our 5 -- 40 micron spectra to archival ISO and Spitzer/IRS observations in order to idenitfy and model longer-term variations for these sources.
Principal Investigator: Lizette Guzman-Ramirez (Leiden Observatory)
Title: Nebular Abundance Discrepancy Problem with SOFIA Part II
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 ~3 higher than the values inferred from collisional lines, with far more extreme values seen in a small number of objects. 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. The very low Te clumps must be cooled predominantly by FS mid-IR lines. We propose to use FORCAST grisms FOR G111, FOR G227, and FOR G329 to map mid-IR FS lines to observe IC 4406, IC 418, NGC 3242, NGC 3132, NGC 2440, NGC 6778, M1-42, and Abell 46 covering a range of adfs from 1.9 to 120. Between cycle 5 (05_0063, PI: Guzman-Ramirez) and cycle 6 (06_0044, PI: Guzman-Ramirez) we obtained FORCAST observations of the PN NGC 7009, following this exact same strategy. Since we have optical MUSE data on the same PN, we are able to compare the emission from the optical with the emission from the IR. We also have a model that reproduces the MUSE data accurately, which is now giving us constraints on the intensities we should see in the IR with SOFIA. We are now preparing a paper with these results, and since this approach is very promising we would like to extend the study to other objects and generalise our results to more PNe.
Principal Investigator: Bringfried Stecklum (TLS Tautenburg)
Title: The Impact of Accretion Bursts from Massive Protostars on their Dusty Environment
Abstract: Our IR monitoring of the S255IR-NIRS3 accretion burst provided direct evidence for the transient heating and subsequent cooling of its circumstellar disk. This new diagnostic yields information on major parameters of the burst as well as disk properties. Recently, two more HMYSO bursts were identified which opens up the possibility to look for differences and commonalities in the small but growing HMYSO burst sample. In mid-January 2019, flaring of the 6.7 GHz CH3OH maser associated with G358.93-0.03 alerted an ongoing burst which turned out to be extraordinary. Compared to the duration of the two events known to date, it was relatively short but nevertheless excited a wealth of maser transitions, several of them never seen before. Since our NIR imaging did not reveal the burst counterpart and there was no submm/mm flux increase detected with ALMA, the flare origin seemed questionable. Thus, we asked for FIFI-LS DDT to prove the burst presence by detecting elevated FIR fluxes. The luminosity increase seen with SOFIA is the only direct evidence of the burst. The second case, G24.33+0.14, was discovered only very recently and its flare still ramps up. A DDT request will be submitted to observe the first HMYSO burst during its rise. Thus, the current proposal aims at second epoch observations. While these events share major similarities, they differ in various respects which may provide clues on their underlying physics. The absence of a flux increase in the submm/mm for G358 might be due to the short burst duration which probably injected not enough energy to heat the cold disk/envelope regions. Consequently, a near-term decline of the FIR fluxes is expected. The G24 burst, however, seems to be repitetive since a previous flare has been observed in 2011. In order to trace the FIR flux changes we herewith ask for SOFIA follow-up measurements of these sources. Modeling the temporal variation of the spectral energy distribution will provide information both, the transient accretion events and their impact on the circumstellar dust environment. A comparison with predictions from HMYSO burst modeling will be made.
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 radio free-free or hydrogen recombination lines 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. This program is enbled by the uniqueness of thee SOFIA/FIFI-LS system to detect the [OIII] 52 µm line from nearby galaxies and has great synergy with our ongong Herschel/PACS spectroscopy data mining efforts. Graduate student Bo Pengis taking advantage of our observing efforts to undertake a theory-based PhD based on this program so we request status as a Thesis Enabling Program.
Principal Investigator: Paola Caselli (Max-Planck-Insitut fuer extraterrestrische Physik)
Title: OD and the origin of water in protostellar cores
Abstract: We propose the continuation of observations with SOFIA of 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 grainsurface 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.
Principal Investigator: Snezana Stanimirovic (University of Wisconsin-Madison)
Title: Thermal Pressure of the Perseus Molecular Cloud via Velocity Resolved [CII]
Abstract: We propose to use the upGREAT instrument on-board SOFIA to observe 158 micron [CII] and 63 micron [OI] emission in the direction of 5 background radio sources behind the Perseus molecular cloud, for which we have processed HI and OH emission and absorption spectra. The [CII] observations will provide a means to directly measure thermal pressure and volume density of the HI envelope. The thermal pressure measurements will be compared to predictions from theoretical and numerical models, directly testing the hypothesis that molecular clouds form from thermally-unstable HI gas. The [CII] observations will also be used to determine the efficacy of OH as a "CO-Dark" molecular gas tracer and to constrain physical properties in directions where [OI] 63 micron emission is significantly detected.
Principal Investigator: Guido Fuchs (University of Kassel)
Title: High resolution IR observations towards VY Canis Majoris – SiO and SO2 as probes of dynamic regions
Abstract: Context. VY Canis majoris is an extreme oxygen-rich red supergiant with a large infrared excess, making it one of the brightest objects at wavelengths 5 to 20 µm. The star is rapidly losing mass via strong stellar winds. It reveals a dust shell and a rich molecular content close to the star with around 25 molecular species found up to now. There are three distinct dynamical regions with different molecular content, i.e a blue-shifted expansion region, a spherical outflow and a red-shifted directed flow. SiO is a typical spherical outflow molecule, whereas SO2 can be found in the two other regions. Until now, most observations have been performed in the radio and submm wavelengths region, but both molecules should also be observable in the mid-IR. So far only CO and NH3 have been seen in the IR region towards this source – and recently also SiO by our own observations. The infrared detection of SO2 and further investigations on SiO around VY CMa would give new insights into the dynamics of this late type star. Aims. It is our aim to perform high-resolution IR observations using the EXES spectrometer to systematically investigate the molecular content of VY CMa at wavelengths where we expect the silicate bearing molecule SiO and the sulfur bearing molecule SO2. Methods. We propose to use the EXES spectrometer on SOFIA with high spectral resolution (R> 60,000) to target specific regions between 7.07 – 8.31 μm to observe VY CMa and another reference star (e.g. BN) that is used as divisor for telluric features. The high resolution is necessary to resolve the ro-vibrational spectra of the targeted species. Synergies. We recently made observations towards VY CMa using the TEXES instrument on the IRTF observatory covering selected frequency regions between 8.8 µm and 11.6 µm. Partial spectra of molecules like NH3 and SiO could be observed and the molecules clearly identified, yet a full spectral coverage was not possible. Also, some TEXES/IRTF spectra are of insufficient quality due to atmospheric disturbances. Anticipated results. We expect to identify the molecule SO2 in the IR wavelength region in the environment of VY CMa for the first time and to add sufficient data to our existing SiO observations to determine the local physical conditions of this molecule (temperature, density, kinematics).
Principal Investigator: Margaret McAdam (Northern Arizona University)
Title: (16) Psyche: Confirming and quantifying the detections of the rotational heterogeneity, hydrated minerals and/or pyroxene with SOFIA+FORCAST
Abstract: Asteroid (16) Psyche is a complex object that has been theorized to be a metallic world. More recent observations have identified the presence of rotational heterogeneity, a fine-grained regolith, pyroxene and hydrated minerals on its surface. As the target asteroid of the Psyche Mission, understanding this complex body is of great interest to the small bodies community. We propose to obtain rotationally resolved mid-infrared spectroscopy of (16) Psyche using SOFIA+FORCAST to quantify the composition of Psyche’s northern mid-latitude region, to investigate the composition of the light and dark areas in this region and determine the distribution of regolith over the surface. The mid-infrared spectral region, covered by FORCAST, contains distinct spectral absorption features that can quantify the amount of hydrated minerals and the composition of pyroxene. Additionally, thermophysical modeling can be used to determine the thermal inertia over Psyche’s northern mid-latitude region which can indicate the presence of regolith on its surface. The observations may help constrain Psyche’s impact history by identifying the composition of impactors bringing exogenic material to its surface, or potentially the nature of Psyche’s lost mantle material if pyroxene is identified. SOFIA is currently the only facility capable of observing asteroids using Q-band spectroscopy and is thus essential for understanding Psyche in preparation of the Psyche Mission.
Principal Investigator: Jinyi Yang (Steward Observatory; University of Arizona)
Title: Probing IR SED of a Bright, Gravitationally Lensed Quasar in the Reionization Epoch with SOFIA
Abstract: The detections of z>6 quasars indicate the existence of up to (ten) billion M_sun SMBHs at <1 Gyr after the Big Bang, and challenge the theory of SMBH growth in the early Universe. However, the relationship between SMBH accretion and star formation activities in their hosts at early epoch remains to be poorly understood. A key to study the AGN-starburst connection is the quasar SED in the rest-frame mid-infrared (mid-IR), which connects dust emission from the central AGN to that in the star-forming host. There are only limited mid-IR studies of z>6 quasars so far, especially at z>~6.5, due to the faint flux of the most distant sources and the difficulty in conducing observations at these wavelengths. In this proposal, we request SOFIA/HAWC+ observations of a bright, gravitationally lensed quasar at z=6.5, J0439+1634. Boosted by lensing magnification, it is the brightest z>6 quasar known in both optical/NIR and FIR. We have already obtained a series of flux measurements in the rest frame UV-optical, NIR, FIR, and radio. However, without mid-IR measurement, there is currently little constraint on the expected peak of quasar SED, thus resulting in large uncertainties in differentiating AGN and starburst contributions to the SED. A measurement, even an upper limit, at the observed frame 100-300 micron will provide significant improvement. The extreme brightness of this quasar makes it an ideal target for SOFIA. The proposed 154 micron measurement will pinpoint the peak location of the dust continuum and enable a realistic SED modeling of a quasar at z=6.5 for the first time, which will allow detailed studies of dust heating source in this AGN-starburst system. After Herschel, SOFIA is the only telescope that could provide high sensitivity observations in the 100-300 micron range in the foreseeable future. The proposed observations will open a new window to probing the high redshift universe in the mid-IR with SOFIA by using highly magnified lensed sources.
Principal Investigator: Kathleen Kraemer (Boston College)
Title: Water Absorption in Late-Type M Giants
Abstract: We propose to use the high spectral resolution and high sensitivity of EXES on SOFIA to characterize the water absorption features at 6.6-6.7 micron in a sample of M4-M6 giants. We have detected surprisingly strong absorption features from water vapor in late-type M giants in data with much lower spectral resolution from ISO's SWS and Spitzer's IRS. Those spectra 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 much stronger at the higher temperatures in the atmospheres of M giants than in the cooler atmosphere of the Earth. 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. Characterizing the physical properties of the water vapor layer is a key step in understanding the molecular chemistry of stars as they begin to lose mass and produce dust. These data will also allow us to determine the best transitions for spectra from MIRI on JWST, which has better spectral resolution than SWS and IRS but lower than EXES, for use in characterizing the water features in similar stars in other galaxies. We were awarded 5.2 hours hours of EXES time in Cycles 6 and 7; we request 2.3 hours in Cycle 8 to observed the remaining approved targets and complete this study.
Principal Investigator: Robert Gutermuth (University of Massachusetts)
Title: Completing the Protostar Luminosity Function in Cygnus-X with SOFIA/FORCAST Imaging
Abstract: We request SOFIA/FORCAST mid-IR imaging of the bright, confused protostars in the nearby million solar mass star forming complex, Cygnus-X. The data will be combined with extant Spitzer data to enable robust luminosity estimates of these objects in order to complete the high luminosity end of the protostar luminosity function or PLF. Many models produce PLF predictions, thus the huge sample of protostars in Cygnus-X as well as the wide range of star-forming environments it encompasses will yield a powerful new tool to differentiate physical models of star formation. These observations have excellent archival value for planning future JWST MIRI IFU observations to probe envelope properties and shock and outflow morphologies at the inner envelope. In addition, the possibility of FORCAST's retirement after Cycle 8 places considerable urgency on completing these observations in Cycle 8.
Principal Investigator: J.D. Smith (University of Toledo)
Title: Unlocking Far-Infrared Metal Abundances in NGC628
Abstract: Elements heavier than helium make up only a small fraction of the mass of the present day Universe, yet they heavily impact how galaxies and stars form and evolve. The chemical enrichment history of the Universe therefore forms an essential part of any complete understanding of galaxy evolution. The ground-state fine structure of the abundant metals oxygen and nitrogen which are accessible to SOFIA in the far-infrared will play a major role in uncovering this history. [OIII] 88µm is already the highest redshift line ever detected in a galaxy (z=9.1), and both potential future FIR missions SPICA and Origins feature the rise of metals as a chief science case. With the ability to penetrate large columns of obscuration in the dusty galaxies that dominate the peak epoch of star formation, and little sensitivity to the unknown temperature structure of ionized nebulae that has plagued traditional optical strong line metal abundances for decades, FIR abundances offer many powerful advantages. Yet substantial work is still needed locally to take full advantage of this potential. We propose a pilot study of the well-studied galaxy NGC628, targeting a dozen regions drawn from the CHAOS program on the LBT -- the largest, deepest survey of direct spectroscopic optical auroral line metal abundances ever undertaken in the local Universe. Combining SOFIA/FIFI-LS with CHAOS spectroscopy, archival Herschel/PACS and Spitzer/IRS, and even VLA free-free continuum observations of carefully selected regions in NGC628, we will fully develop several interrelated temperature insensitive infrared abundance tools, including direct [OIII] abundances normalized to hydrogen using recombination or free-free emission, and expand and validate the novel O3N3 pure FIR-line abundance relationship. Our ancillary data also include deep optical IFU spectral mapping data, to bridge the resolution divide between the SOFIA and ground-optical surveys.
Principal Investigator: Ian Stephens (Center for Astrophysics | Harvard and Smithsonian)
Title: FIELDMAPS: FIlaments Extremely Long and Dark: A Magnetic Polarization Survey
Abstract: Molecular gas in a galaxy generally follows the spiral arms. In the Milky Way, the densest of this molecular gas can form long, velocity-coherent filaments parallel and in close proximity to the Galactic plane. These filaments are huge, with lengths of 20 to >100 pc and widths of ~1.5 pc. These dense filaments make up the 'skeleton' of molecular gas of the Milky Way - akin to the dark dust lanes seen in nearby spiral galaxies - and thus have been called 'bones.' Our simulations suggest that the bones in the spiral arms are formed via compression of molecular gas in the spiral potential, while bones in the interarm regions are formed via shear. For the early stages of star formation, these bones represent the largest star-forming structures in the Galaxy, and previous studies suggest that magnetic fields are critical to their formation. Our pilot survey of 2 bones show that HAWC+ can detect polarization over large angular extents with modest integration time. However, this sample of two bones is insufficient to make any statistical conclusions on their magnetic field properties. Therefore, to understand how gas collects in the magnetized spiral potential, we propose a legacy survey to probe the magnetic fields across the entire extent of 8 additional bones (for a total of 10). We will use these observations in combination with new magnetohydrodynamical simulations of galactic formation of bones to investigate (1) the role of magnetic fields in the formation of bones, (2) how the field varies between arm and interarm bones, and (3) whether or not fields bend into filaments to build gas flows to the largest gravitational potential well. With the vast database of ancillary data, we will create legacy products (e.g., image/cube cutouts, simulation data, and analysis code) that will be hosted for the public via our website, Dataverse, and GitHub.
Principal Investigator: Ravi Sankrit (Space Telescope Science Institute)
Title: The Long Term Evolution of Silicates in Symbiotic Mira Systems
Abstract: Our goal is to study the long term evolution of silicate dust in the circumstellar envelopes of oxygen-rich symbiotic Miras, which consist of a mass-losing AGB star and a hot, accreting post-AGB or White Dwarf companion. We propose to obtain FORCAST photometric and spectroscopic observations of eight symbiotic Miras, and six non-symbiotic AGB stars as a control sample, all of which have been observed by the International Space Observatory (ISO) and whose mid-infrared spectra exhibit the 10mu-m and 18mu-m silicate features. By comparing the ISO and FORCAST data, we will be able to characterize the changes in the spectral shape of the silicate features. We will model the spectra using the publicly available codes DUSTY, and RADMC-3D in order to obtain the dust properties at both epochs of observation, and thereby determine the physical processes that cause the changes in the silicate emisison. Symbiotic Miras as a class have not been very well studied, and our observations will significantly expand our knowledge of these fascinating systems that are known to undergo nova-like explosions, and may be the lower-mass analogues of systems that eventually explode as Type I-a supernovae. A comparison of the observed changes that occur in the symbiotic systems with those in the non-symbiotic stars in our sample will allow us to determine the effects of the binary interaction on the evolution of silicate dust.
Principal Investigator: Michelle Creech-Eakman (New Mexico Institute of Mining and Technology)
Title: Mid-Infrared Spectra of Mira Variable Atmospheres Observed With EXES
Abstract: One of the outstanding questions in astrophysics is how stars enrich their environments as they reach the end of their lives. This enrichment is vital for new star and planet formation, but our understanding of molecule and dust production in circumstellar environments (CSE) is rudimentary. Mira variables are highly evolved cool stars with regular pulsations that loft enriched material into their surroundings, and this makes them perfect laboratories for studying molecules and dust in stellar environments. We propose to use EXES to observe the atmospheres of 3 oxygen rich (M-type) and 2 carbon rich (C-type) Mira variables. The observations will include several CO2 lines in the M-type Miras, and HCN, and C2H2 lines in the C-type Miras. We will model the observations using the radiative transfer code RADEX, which will allow us to determine physical characteristics of the gas such as density and temperature. These results will augment a previous study done the Spitzer IRS.
Principal Investigator: Nicholas Ballering (University of Virginia)
Title: Lurking Giants: Verifying and Characterizing Nearby Bright Debris Disks
Abstract: We propose a survey program to obtain HAWC+ photometry of eight IRAS-detected bright nearby debris disks. IRAS observations were prone to contamination from background sources, and none of these disks were observed in the far-IR with Spitzer or Herschel, so HAWC+ observations are critical to verify these sources as true debris disks. These bright nearby disks, once verified, are promising targets for future high-resolution imaging in the (sub-)mm with ALMA and in scattered light with HST, ground-based high-contrast instruments, and soon JWST. Nearby bright debris disks have revealed a wealth of information about the architectures, dynamics, and compositions of planetary systems. This SOFIA/HAWC+ program is a crucial stepping stone towards finding the next generation of targets for cutting-edge debris disk science.
Principal Investigator: Maria S. Kirsanova (Institute of Astronomy; Russian Academy of Sciences)
Title: Density structure in PDRs around compact HII regions with the [OI] 63 and 145 micron lines
Abstract: This is resubmission of 07-0122 proposal, Priority Level 3 and Evaluation Grade: Very Good/Good. -- Context: Photodissociation regions (PDRs) around massive O and B-stars have several layers where C+/C/CO dominate in the total carbon budget. Theory predicts, the layers can be distinguished using spatially and spectrally resolved observations of PDRs with simple geometry. In contrast with clumpy environment of old HII regions, geometry of younger compact HII regions might be more regular. The contamination from the non-uniform gas density distribution is less significant on the younger stage because the expansion is faster. -- Aims: We propose to study distribution of gas density using [OI] 63 and 145 micron transitions with SOFIA upGREAT in two PDRs where we previously found the layered structure and detected signature of the expanding motion -- Methods: We will determine optical depth of the [OI] lines and column density of atomic oxygen. We also will compare position-velocity (p-v) diagrams of the [OI] lines with available p-v diagram based on SOFIA [CII] 158 micron data and explore the kinematics of the PDR’s layers. -- Synergies: Observations of two [OI] lines, together with the complemented [CII] data, allow us to explore the main cooling lines and shock tracers in the gas around the early-type B-stars. SOFIA GREAT provides a unique possibility for this type of study. -- Anticipated Results: Spatial distribution of atomic oxygen column density will allow us to study density distribution on the PDRs because the [OI] line emission is a tracer of high-density gas. We also will compare the C column with columns of C+ and CO to explore the C+/C/CO transition in the PDRs and find contribution of atomic carbon in the total carbon budget of the PDRs.
Principal Investigator: Conor Nixon (NASA Goddard Space Flight Center)
Title: A Search for Complex Molecules in Titan's Atmosphere
Abstract: We propose to attempt first detections of three previously unseen molecules in Titan's atmosphere. These include one cyclic/aromatic molecule (pyridine) and two heavy linear/aliphatic molecules (C6H2, C4N2). Our proposed investigation utilizes SOFIA’s unique ability to access the far infrared spectrum exhibited by Titan’s cold atmosphere, with all of our target species at 16-25 microns, a region that has poor transmission for ground-based spectrometers (e.g. IRTF/TEXES). This far-infrared spectral region exhibits low-energy C-H bending modes for both linear and cyclic molecules that are ideal for making unique structural identifications. Confirmation of these molecules is of high scientific significance, since Cassini mass spectra have indicated hints of their existence in Titan's ionosphere. Moreover, nitrogen-heterocyclic molecules such as pyridine have high astrobiological importance due to their similarity to backbone rings of DNA nucleobases. Detection of these molecules will help to elucidate the chemical pathways that connect from the plethora of small molecules currently identified in Titan’s neutral atmosphere and provide constraints for photochemical models.
Principal Investigator: Michael Gregg (U.C. Davis)
Title: Detecting the Interstellar Medium of Globular Clusters
Abstract: Milky Way globular clusters are swept clean of any intracluster gas and dust by passing through the Galactic disk ISM. During the 100 million year interval between such disk passages, a typical cluster will accumulate about 100 solar masses of gas from mass loss from evolved red and asymptotic giants, most of which should be retained by the gravity of the cluster. This material has yet to be detected and the fate of the stellar mass loss remains a mystery. This proposal requests time with FIFI-LS to observe a sample of three Milky Way globular clusters predicted by new models to have appreciable gas. The primary aim is to detect and measure the strength of [CII] 158 micron emission to derive the properties of the interstellar material. Because [CII] is 10-100 times more sensitive than other methods, these far-IR observations have a better chance of detecting the ISM in globulars, and will at least establish new upper limits. With robust detections, other emission lines may be measurable, aiding in the determination of the temperature, density, and state of the globular cluster ISM.
Principal Investigator: B-G Andersson (SOFIA Science Center)
Title: Spinning at the Bar - The B-RAT to k-RAT transition in the Orion Bar
Abstract: Dust-induced polarization provides a powerful tool to probe interstellar and circumstellar magnetic fields if the details of the grain alignment mechanism can be fully understood. Radiative Alignment Torque (RAT) theory provides a quantitative framework for this understanding, but some aspects still needs to be quantitatively tested. One such aspect is the possibility that the reference direction for the alignment may change from the magnetic field ("B-RAT") to the radiation field k-vector ("k-RAT") in areas of strong radiation fields. Such direction changes have been claimed for protostellar disks, with CARMA and ALMA observations, and in the Orion Bar, based on earlier SOFIA/HAWC+ data, but have only been qualitatively analysed. While the Orion Bar provides a much better characterized model system to compare to ab initio RAT theory, the existing observations (Chuss et al 2019) were acquired in chop-nod mode and are therefore prone to poorly characterized off-beam contamination. Because the level of polarization in the Bar is low, the position angle rotation seen is therefore insecure. Here, we propose to re-observe the Bar and an adjacent low flux area South East of it, in scan-pol mode, to confirm the possible position angle rotation and allow detailed characterization of the transition from B-RAT to k-RAT alignment based on ab initio RAT theory.
Principal Investigator: Nicole Karnath (SOFIA Science Center)
Title: Magnetic Fields of the Youngest Protostars in the Orion Molecular Clouds
Abstract: The formation of a protostar requires a complex interaction of multiple processes, including magnetic fields. With polarimeters like HAWC+, observations of dust polarization of molecular clouds have revealed the complexity of magnetic field structures and inferred their significance in star formation on sub-parsec scales. In this proposal, we aim to observe three of the four youngest protostars known to date in the Orion Molecular Clouds with HAWC+ at 214 microns. We will measure dust polarization at 19" resolution (~0.04 pc scales) to trace the magnetic field structure from the scales of the cloud down to the scales of individual protostellar cores. These observations will reveal how magnetic fields guide the flow of matter from the clouds to protostars. The HAWC+ observations proposed here will complement existing ALMA and VLA continuum and molecular line data for these targets and upcoming 870 micron dust polarization observations from ALMA at 1'' resolution of ~60 Class 0 protostars. This project will also complement previous Cycle 6 HAWC+ observations of NGC 2068 and 2071. We will use the multi-scale and multi-wavelength data to determine whether or not magnetic fields are dynamically important to the star formation process. We will build up a statistically robust sample of ~50 protostars ranging in evolutionary stages in a single cloud.
Principal Investigator: Edward J. Montiel (SOFIA/USRA)
Title: Sampling the Time Evolution of the Circumstellar Chemistry During the Proto-planetary Nebula Phase
Abstract: Proto-planetary nebulae (PPNe) is an ephemeral phase between the longer lived AGB and PN stages of a star's lifecycle. During this period the inner regions of the former AGB star's circumstellar environment (CSE) begin to be exposed to an increased UV radiation field as the central object evolves into a white dwarf. Great changes in the chemistry of this molecular-rich region is expected to take place as the UV radiation increases over time. Therefore, we are proposing medium to high resolution spectral observations with EXES in order to study how the chemical abundances of the CSE of a sample of carbon-rich PPNe change at various points in their evolution. We have opted to continue to focus on the 7.5 and 13.5 micron region (continuing from 06_0144), because it contains molecules unobservable from the ground and/or with no permanent dipole moment. Previous spectroscopic studies in the mid-IR spectrographs have 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 spectral will be compared to see if any temporal evolution exists and identified 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.
Principal Investigator: Edward J. Montiel (SOFIA/USRA)
Title: Determining How Mass--Lost Rates Impact the Chemical Abundances of Circumstellar Envelopes
Abstract: This is a resubmission of proposal 06_0144, which was rated as "Excellent/Very good", but was not fully completed during Cycle 6 due to extended SOFIA maintenance and a US government shutdown, which cancelled at least two EXES flight series. These observations leave the EXES target pool after Cycle 7. 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 ~ 70,000) 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.
Principal Investigator: James Sinclair (Jet Propulsion Laboratory/Caltech)
Title: Evolution of auroral heating and chemistry at Jupiter's high latitudes
Abstract: Heating and chemistry related to auroral processes represent the dominant forcing of neutral stratospheric conditions at Jupiter’s high latitudes. In regions coincident with the X-ray, ultraviolet and near-infrared auroral emission, strong enhancements in temperature of up to 20 K and enriched concentrations of C2H2, C2H4 and other stratospheric hydrocarbons are observed. This demonstrates that the influx of charged particles modifies the thermal structure and chemistry with respect to lower latitudes. We propose to measure spatially-resolved high spectral resolution spectra of Jupiter’s high latitudes using EXES (Echelon Cross Echelle Spectograph) on SOFIA in order to advance our understanding of how auroral processes modify Jupiter's thermal structure and composition. We will measure the spectra of Jupiter's high latitudes in the Q-branch of CH4 (~1305 cm-1), CH3 (~606 cm-1) and C3H4 (~634 cm-1), which are challenging/impossible to measure from lower altitude observatories. The spectra will be inverted in order to derive 3-dimensional (latitude, longitude, altitude) distributions of temperature, C3H4 and CH3. This information will address hypotheses of how Jupiter's chemistry is altered by the influx of energetic particles, confirm findings by the Juno mission and support ion-neutral chemistry modelling efforts by co-investigators. A comparison with similar measurements scheduled in Cycle 7 will highlight the variability of the thermal structure and chemistry in Jupiter's auroral stratosphere.
Principal Investigator: Noel Richardson (Embry-Riddle Aeronautical University)
Title: The Current Dusty Outburst of the Long-Period Binary WR125
Abstract: We propose to obtain SOFIA/FORCAST spectroscopy of the long-period WC binary, WR 125. Recent infrared observations detected that the star began a new dust-producing episode which seems to be identical to the last outburst in 1992-1994, implying a binary period of 28 years. Many observational characteristics of the system are similar to that of the archetypical WC binary, WR 140. Unlike WR 140, the outburst takes a long two-year period to rach peak flux. During this time period, which corresponds to the upcoming cycle 8 for SOFIA, the dust is just beginning to form, and allows us a unique time frame to obtain mid-infrared spectroscopy of the source - allowing us to identify the precursor molecular features of the dust created in these systems. No other periodic WC binary has had these kinds of measurements made previously, so the proposed SOFIA observations will be an invaluable tool in our understanding of Wolf-Rayet dust in the JWST era.
Principal Investigator: Rebecca Levy (University of Maryland)
Title: The GREAT Cigar: Mapping [CII] in the Disk and Outflow of M82
Abstract: How star formation driven outflows and feedback affect galaxy evolution is major open question with implications for observations and theory. The [CII] 158 micron fine-structure line is a major coolant of the interstellar medium (ISM) and can originate from the ionized, neutral, and molecular components. We can, therefore, use the [CII] line to better understand the multiphase nature of outflow properties and structure. We propose to use upGREAT on board SOFIA to observe the [CII] 158 micron transition at unprecedented spectral resolution in the center and southern outflow of the nearby starburst galaxy M82. M82 is an archetypal example of a large-scale starburst-driven outflow, making it an ideal laboratory for this study. The key science questions that these data will answer are: (1) What are the physical conditions of the gas in M82, and how does it cool? (2) Does the outflowing [CII] decelerate like the HI? (3) How do the [CII] kinematics compare to other ISM phases in the disk? (4) What fraction of the [CII] comes from the different ISM phases? Only SOFIA has the capabi ities to spatially and spectrally resolve the [CII] 158 micron line in the nearby universe. upGREAT allows for both on-the-fly mapping of the center of the galaxy and single pointings along the outflow. M82 is the most well-studied starburst driving a galactic wind in the local Universe. Herschel PACS observed [CII] in M82, but with limited velocity resolution (~240 km/s) and only out to ~1 kpc from the disk (Contursi+13, Herrera-Camus+18). The spatially and spectrally resolved cubes of the center and southern outflow of M82 will be highly complementary to the rich dataset already available (e.g. Leroy+15). The science-ready data products will be released at the time of publication for use by the community. This is a resubmission of our Cycle 7 proposal, which was accepted at Priority 2.
Principal Investigator: Andreea Petric (Institute for Astronomy; UH)
Title: Star-formation efficiencies in nearby, optically luminous Quasars
Abstract: Most bulge-dominated galaxies have at their centers black holes with masses that tightly correlate with the masses of their hosts' bulges. This may indicate that the black holes may regulate galaxy growth, or vice versa, or that they may grow in lock-step. The quest to understand how, when, and where those black-holes formed motivates much of extragalactic astronomy. The [CII] 157.74 micron fine structure line of singly ionzed carbon has been calibrated both as a measure of star-formation rates and as a way to estimate the star-formation efficiencies. Recent SOFIA observations of [CII] in nearby low-luminosity AGN suggest that: high ratios of [CII] to FIR may be associated with obscured AGN outflows and that the [CIII] may be at the interface between warm and cold gas in those outflows. The observations we propose here will test whether luminous, obscured AGN have higher [CII]/FIR ratios than luminous, non-obscured AGN.
Principal Investigator: Jose Pable Fonfria (IFF-CSIC)
Title: Searching for C4 in the C-rich AGB stars IRC+10216 and Y CVn
Abstract: To date, more than 200 molecules have been found in different environments such as molecular clouds or circumstellar envelopes, some of them as large as C70. Molecules are involved in many physical processes that significantly affect the dynamical behavior and the evolution of large scale structures or systems as, e.g., the circumstellar envelopes of the Asymptotic Giant Branch stars (AGBs). The chemistry of these objects has been tried to be explained for a long time but only the formation routes of the most abundant molecules are really understood. Of particular interest, the chemical reactions involved in the growing of different molecules such as the carbon chains, Cn. Some members of this family have been detected in the C-rich AGB stars IRC+10216 and Y CVn, which display optically thick and thin envelopes, respectively. In particular, C2, C3 and C5 are in IRC+10216 with a medium to low abundance and C2 and C3 in Y CVn with a high abundance. The chemical models suggest that the column density of the members of this family decreases when the number of carbon atoms grow. This means that C4 is expected to be in the envelopes of both stars but C4 has not been observed in space so far. A few years ago, we found several weak ro-vibrational lines in a survey carried out with EXES of IRC+10216 around 6.456µm that could be lines of the C4 band nu3. In order to explore the frequency range where these lines were found and aiming to discover C4 in space, we propose to observe IRC+10216 and Y CVn at 6.456µm with EXES in its High_Medium configuration, good S/N ratios and a resolving power higher than 85,000.
Principal Investigator: William Fischer (Space Telescope Science Institute)
Title: Characterizing Outbursting Protostars in Orion
Abstract: A fundamental question in the formation of low-mass stars is how much mass is accreted in episodic bursts of accretion versus steady flows. This has implications for understanding the evolution of accretion onto protostars, the properties of stars as they transition from protostars to pre-main-sequence stars, and the evolution of disks being heated by the bursts. The luminosities and the durations over which they are maintained are crucial factors in evaluating the importance of this mode of star formation. To make progress on this effort, we seek to characterize the luminosities and evolutionary states of six bursts in Orion. Two (HOPS 223 and HOPS 383) are well studied outbursts that were observed with FORCAST in 2015-16. We will revisit them to monitor their evolution since then. The other four were recently discovered in a comparison of 2004 and 2017 Spitzer images at 4.5 microns. The SOFIA photometry will provide firm estimates of the current luminosities and, in concert with previous data, allow an evaluation of the burst durations.
Principal Investigator: Uma Gorti (SETI Institute/NASA Ames)
Title: Tracing cool disk winds with the [OI] 63 micron line
Abstract: Accretion and accompanying winds and outflows drive the evolution of protoplanetary disk masses and dictate planet formation timescales, but the underlying physical processes are poorly understood. Current wind tracers can only probe ~ 5000-10000 K gas and may not be sensitive to radii where most of the mass loss occurs. Therefore, the relative importance of viscous accretion vs. disk winds/outflows is unknown and the efficiency of angular momentum extraction and disk lifetime estimates are uncertain by nearly an order of magnitude. The proposed project is a pilot study aimed at detecting and characterizing a possible cool component of a T Tauri disk wind. Our goal is to use the OI 63µm line to detect a cool wind counterpart to the jet and hot wind seen in optical forbidden lines from the protoplanetary disk around AS 205N. If most of the mass loss occurs in a wind that is too cold to excite the optical lines, then current estimates of the mass loss rate will increase by an order of magnitude becoming close to the mass accretion rate, with implications for angular momentum transport efficiency in disks. The very high resolving power of GREAT can easily isolate the jet and wind components and establish the presence or absence of a cooler wind. We will use theoretical models to analyze and interpret the line profiles, and with available ancillary data determine the wind emitting region and mass loss rate.
Principal Investigator: Georgia V. Panopoulou (California Institute of Technology)
Title: Studying the role of the magnetic field in the atomic-to-molecular transition in the diffuse interstellar medium
Abstract: The initial conditions for the star formation process are set in the very early stages of the evolution of interstellar clouds. Molecular clouds, which are the precursors of stars, form out of the diffuse atomic medium. The physical properties in the atomic-to-molecular phase transition are not well understood. We wish to study the effect of the magnetic field in this process. We have selected a region where such a transition occurs. We use observations of the magnetic field and gas in order to explore their connection during this transition. The FIFI-LS spectrometer of SOFIA will allow us to obtain CII measurements in that region and probe the "hidden" H2 and the total gas volume density. SOFIA observations will complement an array of starlight polarization data, measurements of the Zeeman effect in the HI line, spectroscopic observations of the HI and CO lines that are already available. The proposed investigation will enable an accurate characterization of the dynamic interaction of the local magnetic field with the atomic and molecular diffuse medium.
Principal Investigator: Laura Lenkic (University of Maryland)
Title: Local Analogues of Turbulent, Clumpy, Main-Sequence Galaxies at the Peak of Cosmic Star Formation
Abstract: This proposal aims to characterize the properties of the neutral gas and HII regions in a sample of nearby, clumpy, turbulent galaxies. The properties of these galaxies most closely resemble those of z ~ 1 – 3 galaxies, when star formation activity was at its peak. The galaxies selected for this proposal are from the DYNAMO sample of galaxies from Green et al. (2010). Their disks have high internal velocity dispersions and high gas mass fractions much like z ~ 1 – 3 galaxies, and have star formation rates ranging from 10 to 80 solar masses per year. This gives us a unique opportunity to study the neutral interstellar medium in this turbulent, clumpy environment, without the difficulties that are encountered in high redshift studies. We will use FIFI-LS to observe the 157.7 μm [CII] and 88 μm [OIII]/63 μm [OI] fine-structure lines, and use HAWC+ observations in band C, D, and E to derive the total far-infrared luminosities and estimate the FIR dust temperatures. We will use the combination of [CII] and FIR observations to do photodissociation region modeling and derive the gas densities and far-ultraviolet radiation field strengths, and [OIII] to study the properties of HII regions. We will also derive star formation rates from the total FIR luminosity and use these to test [CII], [OIII], and[OI] as star formation rate tracers. These lines are observable by instruments such as ALMA at higher redshift and are potentially powerful probes of the ISM and tracers or star formation. This proposal is part of a larger multi-wavelength study of DYNAMO galaxies which includes observations from ALMA, NOEMA, Keck, Gemini, and HST. This is also a thesis enabling proposal and thus the SOFIA observations will be a large part of a PhD student thesis work.
Principal Investigator: Umut Yildiz (Jet Propulsion Laboratory)
Title: Where is the Oxygen in high-mass protostars?
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 five high-mass protostars in small maps to specifically be able to quantify any changes in the oxygen chemistry as a function of position, and to be able to convolve the data to the 20$''$ resolution of our H$_2$O observations with Herschel. 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 observations will be compared to lower-mass protostars where the role of UV-radiation is smaller. 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 sequence of how feedback evolves with mass.
Principal Investigator: Tanio Diaz-Santos (Universidad Diego Portales)
Title: A Pilot Survey of Higly Ionized Lines in Low-Metallicity Nearby Galaxies
Abstract: The search for the most distant galaxies is currently one of the main science drivers of any next-generation telescope. In this sense, the Atacama Large Millimeter/Sub-millimeter Array (ALMA) has proven to be extremely successful in the identification of galaxies living at the epoch of reionization (EoR), z > 7, mostly using the [OIII] 88μm fine-structure emission line. Our knowledge about the gas properties of these system is, however, very scarce, and it is only a matter of time that other adjacent lines, such as [OIII] 52μm and [NIII] 57μm, will be used to infer them. Surprisingly, only a few nearby low-metallicity galaxies have Herschel observations of the [NIII] 57μm line, and none has been observed in [OIII] 52μm, implying that there is no local reference point for interpreting the physical properties of galaxies at the EoR. Here we propose a pilot study to observe the [OIII] 52μm and [NIII] 57μm fine-structure emission lines in 4 nearby galaxies spanning more than an order of magnitude in metallicity, and with already available Herschel/PACS observations in the [OIII] 88μm, [OI] 63μm and [CII] 158μm lines. The goal is to 1) study the physical properties of the gas that can be derived from the combination of these highly ionized lines, 2) test the [OIII]52/[NIII]57 ratio as a far-IR metallicity estimator, and 3) provide a local benchmark for the comparison with the most distant galaxies that ALMA will be detecting during the next years.
Principal Investigator: Thomas Giesen (University of Kassel)
Title: Linear C3 - a novel probe to measure the 12C/13C ratio of the Galaxy
Abstract: Context. Carbon molecules and their 13C-isotopologues are commonly used to determine the 12C/13C abundance ratios in stellar and interstellar objects. In two previous SOFIA observation campaigns we successfully observed for the first time the 13C-substituted species 13CCC and C13CC. By comparing the derived column densities to those of the CCC main isotopologue we determined the 12C/13C ratio at the galactic of 25+/-5, which is higher than the value given by Belloche et al 2013, but which agrees within the given uncertainties. Aims. Our aim is to extend the data set of measured ro-vibrational transitions of 13CCC and C13CC to higher J-quantum numbers to derive more precise 13CCC and C13CC column densities and finally a more accurate 12C/13C isotope ratio. Methods. We propose to use the GREAT/upGREAT receiver on SOFIA to search for new ro-vibrational absorption lines of C13CC and 13CCC along the line of sight towards SgrB2(M). Excitation temperatures will be derived from the measured line intensities of C13CC. We chose appropriate settings which will include pairs of 13CCC and C13CC lines within a small frequency range. This will reduce the uncertainties of measured relative line intensities of the isotopologues and will significantly improve the accuracy of the 12C/13C abundance ratios. Synergies. The new results together with previously measured Q(2) and Q(4) transitions of 13CCC and C13CC will allow to derive a more accurate value of the 12C/13C ratio at the galactic center and give insights into isotopic shift effects caused by differences in the zero-point energy of the isotopologues. Anticipated results. We will perform a global data analysis of new and already available data of CCC, 13CCC and C13CC to derive accurate temperatures, column densities and isotopic shifts. We will discuss to what extend the pure carbon chain molecule is suited as a new sensitive probe to determine 12C/13C abundance ratios in carbon rich environments of the galaxy.
Principal Investigator: Brandon Marshall (University of Nebraska at Kearney)
Title: Searching for Herbig Oe stars in the Mid Infrared
Abstract: Models suggest that during the formation process of massive stars the still accreting protostar generates enough radiation pressure to halt or even reverse spherically symmetric collapse directly onto the protostar when it reaches masses of 8-10 M. The leading theory for how these protostars can continue gaining mass is through accretion viaa circumstellar disk feeding mass onto the star. The timescales for disk destruction by a high-mass star indicate that the inner/warm disk survives much longer than the outer/cool disk, suggesting that we are much more likely to detect a remnant disk in the infrared rather than the submm. By finding signs of a remnant disk around recently formed massive stars we hope to show that some Oe-type stars are better thought of as "Herbig" Oe stars, analogous to lower-mass Herbig AeBe type stars, where the emission is associated with a remnant accretion disk rather than circumstellar material associated with mass loss. We will obtain MIR observations of late O-type stars to confirm whether these young massive stars do harbor a remnant accretion disk. Further observations should beable to detect the warm remnant disk by observing excess MIR emission, where current observations have not had the resolution to accurately distinguish stellar and nebular emission at longer MIR wavelengths. With MIR data from SOFIA along with optical and IR spectra we can more accurately model the circumstellar environment. We will use the FORCAST to obtain MIR photometry. FORCAST has higher resolution than WISE and also has wavelength coverage extending further into the infrared. This will allow us to build more accurate and extensive spectral energy distributions (SEDs) for comparison with models. Data taken will be used to build more complete SEDs in the MIR for the sample of stars to compliment stellar spectra taken with Gemini, DAO, WIRO. The project has the potential to improve our understanding of early stages of star formation and the evolution of high-mass stellar accretion disks.
Principal Investigator: Rebecca Pitts (Niels Bohr Institute; Copenhagen University)
Title: Neutral Atomic Sulfur in Cygnus-X: Key to the Missing Sulfur Problem?
Abstract: Context. Sulfur is the tenth most abundant element in the universe, and sulfur-bearing species are both eminent shock tracers and important prebiotics. Yet in dense molecular cores, the detectable sulfur-bearing species account for as little as 0.1% of the sulfur budget. This severely limits our ability to use sulfur-bearing species to say anything quantitative about the gas it traces. Neutral atomic sulfur has not been well-explored as an alternative sink because the 25.25 μm [SI] fine structure line is difficult to observe. Aims. With SOFIA-FORCAST, we seek to confirm the detectability of the 25.25 μm [SI] line from eight sources in Cygnus-X that also have their sulfur-bearing molecular content accounted for through our previous observations with the SMA. We plan to combine study of the atomic and molecular sulfur-budget toward these protostars, shedding light on the sulfur-budget in an unprecedented manner. Methods. By targeting the [SI] line with FORCAST, we intend to detect the line toward the protostellar sources. Measured fluxes will be compared to emission from molecular sulfur-species. To estimate the amount of atomic sulfur, we will compare observations to shock models developed by us. Finally, the combined atomic and molecular sulfur-dataset will be compared to lab experiments where the physical and chemical conditions are simulated. Synergies. These data compliment SMA observations of the same objects as traced by a variety of sulfur-bearing and other molecular species. These and the SMA data comprise the PILS-Cygnus sample. As mentioned above, the proposed shares synergies with lab experiments and shock modeling. Finally, we intend for this to be a pilot for resolved observations of the same lines with EXES. Anticipated Results. With this unprecedented survey of sulfur-bearing species, atomic and molecular, toward a sample of protostars located in a single cloud, we expect to make significant headway in determining the complete sulfur-budget toward star-forming regions. The results will also inform on new laboratory experiments to be carried out by our team.
Principal Investigator: Rafael Eufrasio (University of Arkansas)
Title: Local Analogs to z~10 Galaxies with SOFIA HAWC+
Abstract: Detailed observational data from high redshift objects is difficult and sometimes impossible to acquire, hence the need to select 'local analogs' to high redshift galaxies. We have recently selected the brightest analogs to z~10 galaxies, epoch when high-mass X-ray binaries are expected to be the main source of heating to the neutral intergalactic medium (IGM) prior to the epoch of reionization. Our objectives are to (1) measure the star formation histories (and therefore SFR, Mstar, total infrared luminosities, etc.) via detailed UV-to-FIR SED fitting, (2) measure the XRB SED shape and normalization scaling with SFR, quantify the scatter in this relation, as is required for interpretation of 21 cm measurements of the z > 8 IGM, and establish an empirical metallicity-dependent HMXB population X-ray SED that will be a critical constraint for population synthesis models and the plan- ning of future X-ray observatories that will directly study high-redshift galaxy populations (e.g., Lynx). We propose a time-efficient observing strategy that utilizes bands C and D of HAWC+ to derive the total IR emission of these 30 galaxies. SOFIA data will be combined with archival GALEX, SDSS, 2MASS, and WISE to derive the SFHs of these galaxies, via detailed SED fitting with the LIGHTNING code. SOFIA is essential for our work, as it will give us a handle on the total FIR luminosity, which is needed to constrain the UV-optical attenuation, and therefore a reliable SFR. This sample composes a large Chandra program and it is being observed in X-rays. These galaxies are all present in GALEX, SDSS, 2MASS, and WISE and we will combine this X-ray to Far-IR data in a single analysis. None of these galaxies were detected by IRAS or observed with Herschel, which presents a great opportunity for using SOFIA. In the future, we will propose these galaxies to ALMA, HST, and Swift. A large, panchromatic set of products will be made available to the astronomy community.
Principal Investigator: Michael Gregg (U.C. Davis)
Title: Far-IR Observations of Ram Pressure Stripping in the Coma Cluster
Abstract: This proposal requests time to use FIFI-LS to obtain far-IR spectroscopy of three spirals undergoing spectacular ram pressure stripping in the Coma cluster. These will be the first such observations specifically targeting ram pressure stripping events in a rich cluster. Characterizing far-IR emission lines, particularly 158micron [CII] line, will lead to greater understanding of the formation of the hot intracluster gas in clusters, the morphological transformation of the individual galaxies, and will aid in interpretation of far-IR observations of galaxies in much higher redshift environments.
Principal Investigator: Xin Liu (University of Illinois at Urbana-Champaign)
Title: Resolving Torus Emission in A Kpc-Scale Triple AGN with SOFIA/FORCAST
Abstract: Triple AGN are a natural prediction of LCDM cosmology. They are also important gravitational wave sources. Yet no robust case of triple AGN was known. We propose to image the best known case of a kpc-scale triple AGN with SOFIA/FORCAST. The target is unique in that all three nuclei are optically classified as Type 2 (i.e., obscured) Seyferts. Complementary multi-wavelength observations from the HST, Chandra, and VLA strongly suggest that all three nuclei host AGN, but existing data still cannot determine the relative contribution from AGN, starburst, and/or shock heating conclusively. Only with FORCAST high-resolution imaging will we be able to detect and resolve the two brightest and perhaps all three nuclei in the MIR to constrain the spectral energy distributions to disentangle AGN from starburst and/or shock heating. The results will help understand the torus emission and physical properties of the first kpc-scale triple AGN. It would be a remarkable SOFIA discovery.
Principal Investigator: C. Darren Dowell (Jet Propulsion Laboratory)
Title: Magnetic Field Structure of the Grand-Design Spiral Galaxy M51
Abstract: We propose a deep HAWC+ polarization map of the grand-design spiral galaxy M51, following up very successful exploratory HAWC+ observations of M51 and other nearby, IR-bright galaxies within the past two years. Far-IR polarimetry has now been demonstrated to be a viable technique for tracing the magnetic field in the neutral medium of other dusty galaxies. In M51 (at the current depth) and NGC1068, the field closely follows the spiral arms, but provides hints of underlying substructure. In this proposal, we plan to integrate 2.5 times deeper, which should produce an unprecedented polarization map of long-term value with several hundred resolution elements. We will use this map to test models of the formation of spiral arms, spurs, and magnetic fields themselves.