- SOFIA Overview
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SOFIA Cycle 2 Approved Programs
Proposal ID: 02_0004
Principal Investigator: Graham Harper (University of Dublin, Trinity College)
Title: Probing Betelgeuse’s extended atmosphere with SOFIA-EXES; exploiting the forbidden Fe II ladder
Abstract: SOFIA-EXES provides a unique opportunity to probe the velocity fields and temperatures in the extended and expanding atmospheres of early-type M supergiants. These stars are important for unravelling the poorly understood mass loss process; they have little dust and low molecular abundances, but still drive high mass-loss rates like their dusty cousins of later spectral-types. SOFIA-EXES and IRTF-TEXES mid-IR R=50,000 emission line spectroscopy of forbidden line profiles from each of the first three terms of Fe II would permit us to measure the dynamics from the two hot chromospheric features recently discovered with eMERLIN. The three lines, from the dominant ionization species, sample the chromosphere, the wind acceleration region, and beyond to the circumstellar envelope in the ground term line. These spatial scales correspond to the mass loss during the last 100 years.
Proposal ID: 02_0005
Principal Investigator: Diane Wooden (NASA Ames Research Center)
Title: FORCAST Observations of Comet Siding Spring -- Mars Encounter
Abstract: Comet C/2013 A1 (Siding Spring) will have a near-flyby of Mars on 2014 October 19 18:41 UT. Currently, the odds of a comet-Mars impact are 1:2000 and the closest approach distance is 1.2E5 km. The comet’s trajectory could change by non-gravitational forces or the nucleus could split and make the encounter more dramatic for Mars assets. If the closest approach distance is about 5 times closer then comet material may impinge on the Martian upper atmosphere. Comet Siding Spring -- Mars encounter is a unique opportunity to study a comet that near-grazes Mars, to ask whether there are measurable long term affects on the Martian atmosphere, and for Mars missions’ rovers and orbiters to study an Oort cloud comet at unprecedented close distances and high spatial scales. We propose to observe comet Siding Spring near the time of the Mars-encounter with SOFIA(+FORCAST) to characterize the dust properties of comet Siding Spring to set this comet in the context of other comets, to deepen our understanding of comet origins, and to provide a SOFIA legacy data set for comparison and cross-calibration with data from Mars assets taken in non-standard configurations. SOFIA(+FORCAST) has the sensitivity, spatial resolution and broad wavelength coverage to measure (at SNR>=10) features from organics in the 5-8 micron range and all crystalline forsterite features (11, 19, 23.5, and 27.5 micron) needed to constrain the crystal shapes and relative mass fraction of crystals in this Oort cloud comet. FORCAST two-color images reveal how coma structures (jets) are linked to grain sizes through grain color temperatures, sampling a larger area than the slit. The comet silicate crystal fraction is the benchmark for the radial transport models of crystals formed in the inner protoplanetary disk out to comet-forming zones where volatile ices persisted. Comet organics and crystals trace comet origins.
Proposal ID: 02_0009
Principal Investigator: Robert Gehrz (University of Minnesota - Twin Cities)
Title: SOFIA Target of Opportunity (ToO) Observations of Bright Classical Novae in Outburst
Abstract: Galactic classical novae (CNe) contribute to Galactic chemical evolution by injecting dust grains and gases into the interstellar medium (ISM). We have been selected for SOFIA Cycle 1 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 2 to cover the continued temporal development of bright CNe that go into outburst during Cycle 1 and to initiate temporal coverage of bright CNe that go into outburst during Cycle 2. The proposed observations can determine critical physical parameters that characterize the explosion and the effect of CNe on ISM abundances. In particular, our observations will yield the mass ejected, the mineralogy and abundance of the dust grains, and gas phase abundances of CNONeMgAl metals in the ejecta. The 5 to 37 micron spectral range of FORCAST grisms enables complete and simultaneous access to the many dust and gas emission features that must be examined to derive these parameters. Supplemental FLITECAM observations of a dusty ToO nova are requested to assess the hydrocarbon component of nova dust. Any new nova brighter than 8th magnitude at visual maximum can trigger our ToO program when supporting optical/IR ground-based observations indicate that the nova is in 1) a dust formation and growth phase, 2) a coronal emission development phase, or 3) the early free-free expansion phase. The timescales for SOFIA ToO follow-up observations for a nova that triggers our ToO program can range from weeks, months, and years for cases 1) and 2), to days and weeks for case 3).
Proposal ID: 02_0012
Principal Investigator: Imke de Pater (University of California - Berkeley)
Title: Jupiter’s Tropospheric Dynamics from SOFIA Mapping of Temperature, Para-Hydrogen, and Aerosols
Abstract: We request time with FORCAST to observe Jupiter at mid-infrared wavelengths using 17-37 micron spectroscopy of the collisionally-induced H2-He continuum to derive the zonal mean tropospheric temperatures and para-H2 distribution. In addition, we request imaging in discrete filters between 5 and 37 micron to provide spatial context for the spectroscopy. This combination of imaging and spectroscopy will allow us to relate the distribution of aerosols to the rate of upwelling from the deeper troposphere, and will provide the first maps of para-H2 since the Voyager era.
Proposal ID: 02_0015
Principal Investigator: Robert Gehrz (University of Minnesota - Twin Cities)
Title: Dust in the Winds of Proto-planetary Nebulae: RV Tauri Stars and SRd Variables
Abstract: We propose to obtain SOFIA FLITECAM and FORCAST grism spectra to examine the mineralogy of the circumstellar dust in a sample of post asymptotic giant branch yellow supergiants that are believed to be the precursors of proto-planetary nebulae. The proposed program will produce the first self-consistent sampling of the entire 2.8-37.1 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 silicate materials and to test for the presence of hydrocarbon components in the grain materials. 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. Our program stars are all accessible to SOFIA flights that occur from Palmdale, CA during Cycle 2 and a number of them are suitable for viewing during east-bound flight.
Proposal ID: 02_0016
Principal Investigator: William Vacca (Universities Space Research Association)
Title: Disks around Early B Stars
Abstract: Although high mass star formation models predict that massive stars form with rotating accretion disks, direct observational evidence for the presence of these disks around high mass stars is rather scarce. Therefore, observational constraints on the disk structure and physical parameters (and consequently on the theoretical models) are weak and very limited. We propose to observe a small sample of bright early B-type stars which are believed to possess circumstellar accretion disks, based on previous observations, in order to directly detect the disks via their dust emission at MIR wavelengths. In these systems, the in-falling envelopes appear to have dispersed but the circumstellar accretion disks remain. The spectral energy distributions derived from the proposed FORCAST observations will be fit with models of young stars and used to determine the physical characteristics of the disks (sizes, structure, masses, and temperatures) in these sources. SOFIA with FORCAST provides the only means of studying the disks in these young, massive systems at the MIR wavelengths where their signatures are expected to be the strongest.
Proposal ID: 02_0018
Principal Investigator: Paul Goldsmith (Jet Propulsion Laboratory)
Title: Determining the [CII] thickness of the galactic plane with SOFIA/GREAT
Abstract: The structure of the interstellar medium (ISM) is strongly influenced by energetic events, such as supernovae and massive star formation, that blow gas out of the plane, only to have it fall back elsewhere, for example in the form of high velocity clouds (HVCs). Could clouds in the Galactic disk-halo interface be a significant source of hydrogen available for star-formation. If so, the equilibrium between gas being thrown out and that falling back into the disk, which determines the thickness of the gas distribution of the Galactic disk, is a critical factor regulating the star formation rate in the Galaxy. Observations of the HI and CO suggest that the Galactic disk is stratified, with the diffuse atomic gas being present at greater distances above and below the galactic plane compared to the denser molecular clouds. However, how the warm/diffuse and cold/dense atomic gas - the diffuse molecular gas that is not traced by CO (CO-dark H2 gas) - are vertically distributed in the galactic disk is not yet well understood, but this information would provide important constraints on models attempting to explain the life cycle of interstellar matter ands tar formation in the Galactic plane. We propose to use observations of the [CII] 158um line with SOFIA/GREAT in selected cuts through the Galactic disk to determine its thickness in [CII] and to study how the different phases of the interstellar medium are vertically distributed. Our group has studied the radial distribution of different phases of the interstellar medium in the Galactic plane using the [CII] 158 um line (Pineda et al. 2013), but until this point, we could not determine how the [CII] line is vertically distributed due to incomplete vertical sampling. The proposed SOFIA observations therefore will provide fundamental information on the structure of the Milky Way.
Proposal ID: 02_0019
Principal Investigator: Mark Swain (Jet Propulsion Laboratory)
Title: The Origin of non-LTE Emission on Dayside of a hot-Jupiter Exoplanet.
Abstract: Powerfully irradiated, short-period exoplanets can experience a combination of insolation and wind from the stellar primary that provides an environment unlike anything experienced by planets in our own solar system. These extreme environments provide a laboratory for testing our understanding of planetary atmospheres. The report from ground-based observations of strong 3.2 micron emission in the hot-Jupiter HD 189733b, attributed to methane undergoing a non-LTE (Local Thermodynamic Equilibrium) process, has generated considerable discussion. Although non-LTE emission, including methane fluorescence is observed in our own solar system, the strength of the emission in HD 189733b was surprising. The original result has been both challenged and confirmed using ground-based observations that are all potentially subject to contamination by the absorption and variations arising in the troposphere and planetary boundary layer. Theoretical work suggests that non-LTE emission may originate from high J number hot combination bands, however, improved measurements are needed to confirm this. Because the SOFIA observatory operates above the most significantly variable portion of the Earth’s atmosphere, SOFIA/FLITECAM offers a unique opportunity to decisively confirm and probe the physical origin of the strong emission around 3.2 micron. In addition, these SOFIA observations will allow the construction of a two-dimensional spectral image of the day side of HD 189733b and enable the comparison of the spatial distribution of the strong line emission to the continuum.
Proposal ID: 02_0021
Principal Investigator: Aneurin Evans (University of Keele)
Title: The Born-again Phenomenon
Abstract: We will use SOFIA FORCAST and FLITECAM grism observations to obtain the spectral energy distributions of stars that have recently undergone very late thermal pulses. These are very rare, poorly observed, and little understood events that can potentially give us a glimpse of the eventual fate of the Sun. With spectral coverage from 2.6 - 37.1 microns we will be able to determine the mass-loss rate from the central star, its physical state and the nature and extent of its circumstellar dust shell. We will also be able to characterize carriers of the Unidentified Infrared (UIR) emission from those objects displaying such emission. Our observations will throw light on a phase of the evolution of low mass stars that is very poorly understood.
Proposal ID: 02_0027
Principal Investigator: Volker Ossenkopf (Universitaet zu Koeln)
Title: CII mapping of hot gas in S140
Abstract: To understand the dynamical structure of the warm and thin gas in the S140 molecular cloud and the influence of the embedded sources, the sub-mm cores, and the adjacent cluster of B stars on the production and excitation of ionized carbon we propose to map the cloud in the [CII] fine structure transition, covering the same region that has been observed already through IRAM in molecular lines and PACS/Herschel for the dust continuum. The observations are to explain the distribution of the interclump gas, to identify the signature of internal heating sources on the gas and to quantify the the velocity structure of this gas to identify systematic flows, pressure gradients and other indications for the triggering of star formation. We request a total observation time of 1.1h for this map. The L#1 channel is to be used simultaneously to map the CO 13-12 line to trace the extent of warm and dense gas.
Proposal ID: 02_0029
Principal Investigator: Terry Jones (University of Minnesota - Twin Cities)
Title: Massive Star Formation in IRDC G034.43+00.24
Abstract: The study of massive star formation in the cores of Infrared Dark Clouds (IRDCs) is a key part of the science vision for SOFIA. IRDCs are important new laboratories for studying the pristine, undisturbed physical conditions of cluster-forming clouds before they are shredded apart by winds and radiation. We propose to observe two IRDC cores, MM1 and MM3, in G034.43+00.24 with the higher spatial resolution of SOFIA and multiple bandpass capability of FORCAST. MM1 and MM3 have total luminosities comparable to early B stars but it is unknown whether they are forming compact clusters of massive stars, or what stage of evolution they are in. Observing MM1 and MM3 with FORCAST will allow us to determine whether their poorly constrained Mid-IR luminosity is due to multiple sources. We will compare the spectral energy distributions of MM1 and MM3 and if possible any individual sources separable within them, which will provide clues to the evolutionary state of the sources.
Proposal ID: 02_0031
Principal Investigator: Roberta Humphreys (University of Minnesota - Twin Cities)
Title: Cool Dust and the Mass Loss Histories of the Hypergiants
Abstract: A few highly unstable, very massive stars lie on or near the empirical upper luminosity boundary in the HR diagram. They represent a short-lived evolutionary stage, characterized by high mass loss and eruptive events. Many of them are strong infrared sources and powerful OH masers. Space and groundbased visual and near-IR imaging has revealed evidence for asymmetric ejections and multiple high mass loss events in the circumstellar ejecta of VY CMa and IRC+10420, for example. In this proposal, we turn our attention to the cool dust which may or may not spatially coincide with the visual ejecta. It may have formed due to the recent mass loss episodes or be a fossil record of earlier mass loss. Measuring the cold dust will provide a more complete estimate of the total mass lost and the mass loss histories of these stars. We propose imaging from 11.1 to 37 microns with FORCAST of five of these hypergiants.
Proposal ID: 02_0034
Principal Investigator: Jesse Bregman (NASA Ames Research Center)
Title: A Search for Hydrogenated Polycyclic Aromatic Hydrocarbons (Hn-PAHs) in Proto-Planetary Nebula Outflows
Abstract: The high density and low UV intensity environments around the AGB stars and proto-planetary nebulae (PPN) provides an excellent site for manufacturing carbon-based molecules. This material is ejected into the ISM and provides a majority of the carbon to the ISM. Spectra of carbon-rich PPN are complex, and show, among other components, emission from polycyclic aromatic hydrocarbon (PAH; 3.3 and 6.2 microns) and aliphatic compounds (3.4, 6.9, 7.25 microns). In some PPN, emission in the aliphatic 3.4 micron band is unusually strong relative to the 3.3 micron PAH band. Recently, Sandford et al. (2013), based on extensive new laboratory data, have suggested that both the 3.4 and 6.9 micron emission bands attributed to aliphatic molecules could instead arise at least partially from hydrogenated PAHs (Hn-PAHs), and they make specific predictions that we can test by observing PPN that have both high and low 3.4/3.3 micron band ratios. We propose to obtain high resolution FORCAST grism spectra of a sample of five PPN to search for structure in the 6.9 micron feature in PPN that could indicate multiple components, and to accurately measure the relative strengths of the 6.2, 6.9, and 7.26 micron bands with the goal of either measuring, or putting limits on, the relative abundances of aliphatic and Hn-PAH molecules around these stars. These new data will be combined with already existing 3 micron spectra from the literature to determine the presence or absence of Hn-PAHs. Hn-PAHs are expected to be winnowed out (converted to normal PAHs) by interstellar processes and therefore will probably only dominate in early stages of stellar outflows. If we can establish their presence, future work may be able to use their spectral features to probe the PAH formation process.
Proposal ID: 02_0035
Principal Investigator: Enrique Lopez-Rodriguez (University of Texas at San Antonio)
Title: Characterization of the clumpy torus of Active Galactic Nuclei using FORCAST
Abstract: The unified model of Active Galactic Nuclei (AGN) explains the several classes of AGN by an orientation-based model. A geometrically and optically thick torus of gas and dust obscures the central engine in some lines of sight. However, the properties of the torus are still uncertain, and several questions remain unanswered: 1) How is the torus material distributed? 2) How do the properties, such as geometry and distribution of clumps, of the torus depend on the AGN luminosity and/or activity class? Observations at infrared (IR) wavelengths are essential to these investigations as the torus intercepts and re-radiates a substantial amount of flux from the central engine. Near-IR (NIR) and mid-IR (MIR) observations from the ground have been key to advance our knowledge in this field. However, since the atmosphere is opaque to the far-IR (FIR), observations are impossible from ground-based telescopes. Recent Bayesian inference studies suggest that the 30-40 um range provides the largest constraining power for the clumpy torus models, helping to constrain the torus radial extent (Y) and the radial distribution of clumps (q). Thus, FORCAST provides 1) the best angular resolution within the 30-40 um range of the current suite of instruments, crucial to estimate the contribution of the torus emission; and 2) the largest constraining power for the clumpy torus models in the suggested wavelength range, crucial to characterize properties of the torus in AGN. We therefore request FORCAST 31.5 um imaging of 14 nearby, and well-studied, AGN to characterize the torus. We will combine these data with already acquired NIR and MIR data to construct the finest and broadest spectral energy distribution (SED) dominated by torus emission. The combined NIR, MIR and FORCAST data will lead to obtain a complete physical description of the torus in AGN.
Proposal ID: 02_0036
Principal Investigator: B. Holwerda (European Space Agency)
Title: FORCAST observations of Edge-on Spirals
Abstract: The vertical structure of spiral galaxies can best be characterized when the disk is seen edge-on. In such galaxies, the dusty ISM appears to concentrate in the plane of massive disks, In smaller galaxies, the dust clouds are distributed throught the height of the stellar disk. This may well constitute a phase-change with galaxy mass for spiral disks: the surface density in massive disks is sufficient to settle the ISM in a thin disk. In low-mass disks, turbulence spreads the clouds througout the height of the stellar disk. The most comprehensive approach is to fully model the spectral energy distribution across wavelength of resolved edge-on spiral galaxies, tracing the stellar and dust emission. Such models detail the transmission and re-processing of stellar light by dust. A critically missing component are high-resolution mid-infrared maps of the hot dust. SED models currently allow for a degenaracy: the dust disk may be heated partially in the central plane by embedded star-formation or it may be strongly clumped througout the height of the disk with an unknown fraction of clumps heated by star-formation. We ask for FORCAST 19.7 and 31.2 micron observations to resolve the vertical structure of dust heated by embedded star-formation to break this pivotal degeneracy in the SED models for our full sample of 24 edge-on spirals, covering a range of Hubble types and galaxy masses.
Proposal ID: 02_0037
Principal Investigator: Glenn Orton (Jet Propulsion Laboratory)
Title: 17- to 37-micron Photometry and Spectroscopy of Uranus and Neptune
Abstract: We propose photometric and spectroscopic observations of Uranus and Neptune from 17 to 37 microns using the FORCAST instrument. This spectral region includes wavelengths for which there have been no spectroscopic observations, and the combined capabilities of SOFIA and FORCAST are ideally suited to make these observations. The anticipated observations will advance out knowledge of the radiative and convective processes shape the atmospheric dynamics of these two ice giants. They will also determine the extent of para vs. ortho H2 disequilibrium in the upper tropospheres of both planets and improve constraints on the He/H2 ratio. The latter is a crucial value required to eludicate differences in formation mechanisms that distinguish them from the gas giants, Jupiter and Saturn. The proposed observatiosn are also vital for ongoing efforts to develop models for the spectra of both planets as key components of an absolute calibration system used by Herschel spacecraft instruments and other long-wavelength Earth-based observations.
Proposal ID: 02_0038
Principal Investigator: Goran Sandell (NASA Ames Research Center)
Title: [CII] as a tracer of outflows from young high-mass stars
Abstract: [CII] may be one of the best tracers for outflows from young high-mass stars. High mass stars always form in clusters and molecular outflows from such high-mass stars often show overlapping outflows from other nearby cluster members. Here we target high-mass stars, which have already reached the main sequence in the sense that they power ionized outflows, although they are so heavily accreting that they have not yet formed a ‘classical’ HII region. The ionized outflows are observed in radio recombination lines, but these lines are weak and can only be imaged close to the star. Optical and near infrared lines (H alpha, Paschen alpha) are not usable, because these stars form in cloud with hundreds of maginitudes of visual extinction. The fine structure line of carbon, [CII], at 158 micron, is known to be bright in ouflows from high-mass stars and traces gas with higher velocities than what is seen in standard molecular tracers like CO. In this proposal we will map the ionized outflows of two well-studied young high-mass stars and investigate the ionized outflows of another two in order to see whether they are feasible for a mapping study.
Proposal ID: 02_0039
Principal Investigator: Farhad Yusef-Zadeh (Northwestern University)
Title: FORCAST Observations of Sgr C at the Galactic Center
Abstract: The Galactic center molecular cloud Sgr C hosts a cluster of young massive stars and a large concentration of Galactic center magnetized radio filaments. Many of the sources in this cluster suffer from saturation at 24 microns within our MIPS survey. The proposed measurements will study the cluster of YSOs and diffuse filamentary features concentrated in Sgr C and investigate the hypothesis that the nonthermal radio filaments originate in the cluster of young mass-losing stars. To examine this hypothesis, we will use FORCAST to study the SED of individual massive stars, to determine the nature of the diffuse filamentary structures detected at 24micron, to search for weak filamentary structure associated with stellar objects in Sgr C and to determine the massive star formation rate associated with this cluster. There is a critical need for mid-IR observation of highly embedded, saturated stellar sources and its utility in identifying synchrotron emission from young particles associated with Galactic center nonthermal radio filaments. The proposed measurements is a critical test of the scenario in which nonthermal filaments originate in Galactic center star formation regions.
Proposal ID: 02_0045
Principal Investigator: Randolf Klein (Universities Space Research Association)
Title: The Early Evolution of Very Massive Star-Forming Cores
Abstract: Massive stars strongly impact their galaxies, but their formation is not well understood. We propose to observe a minimum of four of the most massive cloud cores (M>1200Msun) from our sample of deeply embedded protostars/proto-clusters as a SOFIA Survey using 6.3hr. The young and very massive cores are selected by their millimeter continuum emission. Data from Spitzer (GLIMPSE) and Herschel (HiGal) indicate very young deeply embedded sources and in two cases possibly starless massive cores. SOFIA offers to provide the missing link between the near and far-infrared data. The Spitzer/MIPS maps of these very massive cores are all saturated or nearly saturated. We propose to use FORCAST with the 11.1, 19.7. 31.5, and 37.1 micron filters. With the sensitivity and resolution of SOFIA and FORCAST, we will be able to probe the embedded source, evaluate the energetics of each region, and model the spectral energy distributions across the infrared and into the millimeter. With these data, we will shed light on the initial properties and the early evolution of massive star forming regions.
Proposal ID: 02_0046
Principal Investigator: Klaus Huber (Universitat Hamburg, Hamburger S)
Title: Do starspots inflate the exoplanet CoRoT-2b?
Abstract: We propose to use SOFIA’s combination of HIPO and FLITECAM to obtain simultaneous optical and infrared transit photometry of the CoRoT-2 system. This system consists of the highly active planet host-star CoRoT-2A and the unusually inflated hot Jupiter CoRoT-2b. CoRoT-2A’s surface is densely covered with starspots, which influence the transit lightcurves and, thus, complicate the determination of accurate planetary parameters. In particular, this can lead to an overestimation of the planetary radius, which could, at least partially, account for the unusually large radius inferred for CoRoT-2b. Using SOFIA, the weaker starspot contrast at longer wavelengths will allow us to derive an accurate planetary radius from infrared photometry and, thereby, pin down CoRoT-2b’s radius anomaly. Because of SOFIA’s unique capability to simultaneously obtain optical photometry, we will also be able to determine starspot temperatures and estimate the total spot-coverage of CoRoT-2A’s surface by comparing the deformation and depth of the infrared and visual-band transit lightcurves. Only SOFIA’s combination of HIPO and FLITECAM provides the quasi space-based high-precision multi-band photometry required to address these open questions on the young planetary system CoRoT-2.
Proposal ID: 02_0048
Principal Investigator: Sarah Ragan (Max-Planck-Institut fur Astronomie, Heidelberg)
Title: Probing for large scale infall along an IRDC filament
Abstract: The current picture of high-mass star formation lacks strong observational constraints on the dominant processes. One pressing question is how do the precursors of massive stars and clusters acquire their mass? Is there evidence of global collapse along filamentary infrared-dark clouds (IRDCs) as current models suggest? SOFIA/GREAT offers a valuable new probe of unambiguously measuring infall rates with absorption of the NH_3 (3-2) rotational line at 1.81THz. We select a well-studied young embedded protostar which shows evidence for a large rotating toroid and contains an outflow driving source. We have structural, temperature and luminosity information from Herschel, and we also have supplementary kinematical data on large and small scales, to fit the measured infall rates into the existing dynamical picture. We propose a pilot study to use the new NH_3 probe to measure the infall rate not only directly associated with the peak of emission, but also at offset positions along the host filament to quantify the importance of infall on parsec scales. This 2.1h project takes the next step in exploring the utility of the NH_3 probe which can distinguish infall unambiguously from other dynamical processes, such as outflows or rotation, within the complex environments where massive stars form.
Proposal ID: 02_0050
Principal Investigator: Alycia Weinberger (Carnegie Institution of Washington)
Title: Watching the Collisional Cascade of a Giant Impact
Abstract: The extreme debris disk of BD+20 307 was probably generated in a giant collision, perhaps akin to giant impacts that shaped the early solar system. This old star hosts a warm ring of dust at 0.85 AU that is orders of magnitude more dusty than any other star its age. Because of its extreme dustiness and the location of its debris so close to the star, the timescales for changes can be years rather than millennia. Stochastic release of small particles and collisions of planetesimals of various compositions over time may change the location, size distribution, and composition of the resulting dust. All of these imprint a signature on the 8-24 micron spectrum. We therefore propose to observe BD+20 307 with FORCAST and compare its spectrum now to those taken with Spitzer three collisional lifetimes ago. BD+20 307 is a rare place where we can actually search for evolution resulting from a giant impact manifested in changes in the composition of the debris with time. Our understanding of collisional cascades comes from aggregate samples of stars at a range of ages. This is an opportunity to test cascade models against a system evolving in real time.
Proposal ID: 02_0053
Principal Investigator: Daniel Angerhausen (Rensselaer Polytechnic Institute)
Title: Exoplanet transits with FLIPO: Is GJ 1214b a water-world Super Earth or a cloudy Mini-Neptune?
Abstract: We propose to use FLIPO on SOFIA to comprehensively analyze the atmospheric composition and temperature structure of the first planet in the super-Earth range to be characterized: the possible water-world GJ 1214b. These observations will allow us to determine the overall structure and the chemical composition of the atmosphere. Our constraints on these aspects of the planetary atmosphere will be achieved through spectrophotometric transmission observations during transit in 2 optical and 2 infrared channels - the 1.90 micron `Paschen alpha cont.’ and 3.05 micron `water ice’ - that are not observable from the ground. Furthermore HIPO and FLITECAM (in the FLIPO configuration) are the only instruments available for simultaneous optical and IR observations: SOFIA has unique capability to provide quasi space-based photometry enabling us to answer the state-of-the-art scientific question whether GJ 1214b is a `water-world’ or a small Neptune-like gas-giant. Our observations will pave the way for future observations of a wide range of exoplanet atmospheres with FLIPO on SOFIA.
Proposal ID: 02_0054
Principal Investigator: Antoine Gusdorf (Observatoire de Paris)
Title: High-J CO observations of PRISMAS Herschel KP sources with GREAT
Abstract: With this proposal we want to observe the CO (16-15) transition towards four strong continuum sources corresponding to regions of massive star formation, and that are targets of the PRISMAS Herschel KP. Such information is paramount to calibrate the already observed PACS CO ladder in such objects and estimate the distribution of the gas in the various kinematical components of the high-J Co transitions. In a second step, excitation temperature and CO column densities can be inferred, and used as constraints on our detail ‘irradiated’ shock modelling. A combination with our complementary observations allow to use this modelling to investigate the physics, chemistry, and energetics of massive star-forming regions, allowing to probe the formation mechanisms and quantify their environmental impact.
Proposal ID: 02_0056
Principal Investigator: Olivier Berne (IRAP)
Title: The evolution of PAH size distribution in the NGC 7023 reflection nebula
Abstract: Broad emission features at 3.3, 6.2, 7.7, and 11.2 um dominate the mid-infrared emission of most astronomical objects. These features are generally attributed to IR fluorescence of UV-pumped Polycyclic Aromatic Hydrocarbon (PAH) molecules. These molecules play key roles in the physics and chemistry of interstellar and circumstellar media. Recently, there has been growing evidence that PAH molecules are processed by UV photons, producing a rich organic chemistry (e.g. fragmentation leading to hydrocarbons, isomerization into fullerenes etc.). It is expected that one signature of this chemistry is the evolution of the size distribution of PAHs with the local physical conditions, especially with UV radiation field. Therefore, dedicated infrared observations are needed to quantitatively constrain the photochemical models describing this evolution of PAH size in the interstellar medium. Here we propose to use FLITECAM and FORCAST in order to directly probe the evolution of the size distribution of PAHs in the NGC 7023 nebula. The wide field of view and selective filters allow to do so, at large scales, for the first time. The total required time for this proposal is 1.17 hour.
Proposal ID: 02_0057
Principal Investigator: Jochen Eisloeffel (Thuringer Landessternwarte Tautenburg (TLS))
Title: The origin of the warm gas in the low-mass L1448 outflow
Abstract: For our understanding of the outflows from young stellar objects it is crucial to know the origin and the kinematics of the warm and dense CO gas (n(H2) = 10^5 - 10^6 cm^-3 and T_kin = 300 - 1000 K) that has a key role in the dynamics and energetics of these flows. This gas has first been observed at the outflow base by ISO, whose poor spatial and spectral resolution, however, prevented one from locating its region of emission. We propose here to observe the CO(16-15), (13-12), and (11-10) lines in the outflow driven by the young and heavily embedded Class 0 protostar L1448-mm with GREAT. Together with available ground-based and Herschel observations of lower-J CO transitions we will be able to test whether the warm gas results from the highly-collimated fast ‘primary’ jet, or it is due to shocks created at the interface between the highly-collimated atomic jet and the cold entrained outflow.
Proposal ID: 02_0058
Principal Investigator: Alexander Tielens (Leiden Observatory)
Title: Physical conditions in the dense molecular clumps of the Cas A supernova remnant
Abstract: There are many indications that supernova ejecta are important contributors to the dust budget of galaxies both locally as well as in the early Universe. The formation of this dust and its protection against the destructive effects of the strong reverse shock processing supernova remnants before they merge with the interstellar medium are not understood. However, likely dense clumps are involved. Spitzer, Akari, and ground-based near- and mid-IR studies of dense clumps in the Cas A supernova remnant have revealed bright emission due to CO but the data was difficult to interpret in terms of physical conditions. Recently, we have detected the pure rotational emission lines of CO from one of these clumps with PACS on the Herschel Space Observatory. These data reveal large column densities (4E19 per square cm) of warm (500-1000K) dense (1E5 to 1E6 particles per cubic cm) molecular gas. Such a dense environment is very conducive to dust formation and protection. However, the relationship of this molecular gas with the ionic gas is unclear and the derived column densities are much larger than shock model predictions, indicating the importance of energy conduction by electrons from the surrounding hot plasma into the clump. Electron energy conduction is a key process in the evolution of dense clumps and drives the overall morphology of supernova remnants and their interaction with the interstellar medium. Here, we propose to observe these clumps in the [OIII] 52&88 microns, [OI] 63 microns, and [CII] 157 microns atomic fine-structure lines with FIFI-LS/SOFIA. We will compare the distribution of these ionic lines with that of the mid-IR CO emitting gas and derive the physical conditions and column densities of the different emission components. The proposed observations are designed to address the key questions: “What are the preshock and postshock conditions in fast moving knots and how well can dust be protected in these knots?", “Are the observed variations in the mid-IR CO emission related to variations in the pre-shock density, column density or the presence of additional heating sources for the gas?", and “What is the importance of electron energy conduction for the heating of the gas?"
Proposal ID: 02_0061
Principal Investigator: Kate Su (University of Arizona)
Title: Nature of the Warm Excess in eps Eri: Asteroid belt or Dragged-in Grains
Abstract: Eps Eri and its debris disk provide a unique opportunity to probe the outer zones of a planetary system, due to its young age (~1 Gyr) and proximity (3.22 pc, the closest prominent debris disk by more than a factor of two). It is the Rosetta Stone for more distant exoplanetary debris systems and thus critical to understanding the mid-term evolution of our Solar System. From resolved images in the far-infrared and submillimeter along with spectra from 10-35 and 55-95 microns, Backman et al. (2009) found that the eps Eridani disk has a complex structure, with multiple zones in both warm (asteroid-like) and cold (KBO-like) components. However, Reidemeister et al. (2011), on the contrary, suggested that the system has one dominant cold belt and the warm excess originates from small grains in the cold disk, which are transported inward by the combination of P-R and stellar wind drags. Although both models fit the disk SED and marginally resolved far-infrared images relatively well, the resultant disk structures in the 15-50 AU range at mid-infrared are expected to be very different. We, therefore, propose to obtain a 35 micron image of the eps Eri system using the FORCAST on SOFIA to test the validity of any models for this zone in eps Eri. No other current and future planned facilities can obtain such a 35 micron image, which will provide general constrains on the nature of the warm excess and any potential shepherding planets and their orbits in this iconic debris system.
Proposal ID: 02_0062
Principal Investigator: Urs Graf (I. Physikalisches Institut, Universitaet zu Koeln)
Title: Spatial variation of the strong [CII] self-absorption towards NGC 2024
Abstract: During “basic-science", we mapped a 3x2.5 square arcmin region towards NGC 2024 in [CII] with GREAT/SOFIA. We find extraordinarily bright [13CII] emission, implying a very high C+ column density, and strong [CII] self-absorption in cool foreground gas. The high intrinsic brightness of C+ from the background indicates a very high excitation temperature, at the upper end of what standard PDR models predict. These findings are in strict contradiction to any HII region-molecular cloud model and are hard to explain even in a very clumpy, fractal structure. They indicate that a good part of the possible chemical processes and excitation conditions for [CII] are poorly understood. The self-absorption hides a high fraction of the emitting gas from detection, which has a severe impact on the [CII] intensity-star formation relation, commonly derived from the integrated line intensity. While the GREAT observations show significant variation with position when smoothed spatially and spectrally, the data do not have sufficient signal to noise to disentangle the details of the self-absorption at the full spatial resolution of 15". The aim of this proposal is to re-observe the region in [CII] to study the origin of the self-absorption at high spatial resolution and better sensitivity. This will allow to resolve the structure and excitation conditions of [CII] prevailing in NGC 2024 and, without doubt, in other star forming regions.
Proposal ID: 02_0063
Principal Investigator: Diane Cormier (Universitat Heidelberg)
Title: Disentangling the ISM phases of the nearby low-metallicity dwarf galaxy NGC4214 using velocity-resolved [CII]
Abstract: We propose to observe the far-infrared (FIR) fine structure line [CII] at 1.9 THz with the instrument GREAT onboard the SOFIA observatory in the nearby irregular dwarf galaxy NGC4214. The goal of this proposal is to unveil the dynamical structure of the [CII]-emitting ISM, and most importantly of the photo-dissociation regions (PDR), in three star-forming regions that exhibit different levels of activity. In combination with high-resolution CO and HI data, that our team has already acquired, this will allow us to characterize the physical properties of these regions, determine the origin of the [CII] emission, dissect the molecular cloud structures, and answer key questions of star formation at low metallicity.
Proposal ID: 02_0064
Principal Investigator: Alessio Caratti o Garatti (Max-Planck-Institut fur Radioastronomie)
Title: Investigating atomic jets in high-mass YSOs
Abstract: Protostellar jets and outflows are ubiquitous phenomena among young stellar objects (YSOs). So far, due to the extremely high visual extinction, the observations of high mass YSO outflows have been mostly restricted to molecular tracers at mm and sub-mm wavelengths, and few attention has been paid to the jet atomic component, produced by fast and strong dissociative shocks. Hower, its detection and study might be the key to understand massive star formation. As largely demonstrated by the detection and analysis of many Herbig-Haro objects in low-mass YSOs, the atomic component is a fundamental coolant of protostellar jets, as much important as its molecular counterpart. Indeed, bright [OI] and [CII] emissions in the far-IR was detected with ISO/LWS in a few massive YSOs, but no follow-up with HERSCHEL/PACS has been performed. Therefore, we propose to investigate the physical properties of the atomic/ionic jet component of HMYSO molecular outflows with FIFI-LS. The simultaneous analysis of the FIFI-LS [OI] and [CII] maps will provide constraints on the excitation mechanisms, and the most important dynamical parameters of the atomic jet will be derived. These, in turn, will be compared with values from the molecular component available in literature.
Proposal ID: 02_0066
Principal Investigator: Andrew Rivkin (The Johns Hopkins University)
Title: Characterization of OH and H2O in Asteroids
Abstract: Decades of observations have demonstrated that OH-bearing minerals exist on some asteroids, and recent work has begun to differentiate between and intepret differing band shapes in the 3-micron spectral region. However, this work is hampered by the inability to detect the OH band center and band depths near 2.7 microns from the ground, critical for determining the minerals present. Furthermore, observations of OH on the lunar surface, believed created by solar wind interactions with lunar regolith, add an additional twist to interpretations of the asteroidal spectra. We propose observations of several bright asteroids, some known to have OH-bearing minerals and some for which none are detected from the ground, in order to achieve the goals of better understanding the distribution of OH on the asteroids, and the origin of that OH.
Proposal ID: 02_0067
Principal Investigator: Ralph Shuping (Space Science Inst.)
Title: SOFIA-FORCAST Observations of Circumstellar Disks in W40
Abstract: We propose to observe 2 Herbig Ae/Be stars and 1 low-mass young stellar object (YSO) in the W40 star forming region using the FORCAST grisms. W40 is one of just a handful of high-mass star forming regions within 1 kpc of the sun and thus provides an important laboratory for understanding the nature of star and cluster properties; very little is known about any of the sources individually. These proposed observations will help us to determine the detailed properties of the circumstellar disks around these three stars, which are the brightest in the region. Mid-IR spectroscopy of these young stellar objects can reveal a wealth of information about the structure, temperature, and geometry of the circumstellar disks. SOFIA-FORCAST is uniquely suited to carry out these observations as the disk emission is expected to peak in the mid-IR, and there are no comparable space-based facilities.
Proposal ID: 02_0070
Principal Investigator: Lee Mundy (University of Maryland College Park)
Title: Star Formation in the Dense Environment of Young Clusters: A FORCAST Imaging Survey
Abstract: [****This is a re-submission from a successful cycle 1 proposal, for which the observations have not yet taken place. We are following the advice from the SOFIA team and re-submitting this proposal, hoping we can still obtain the time on our sources and achieve our scientific goal.****] We propose a multi-wavelength FORCAST survey of 6-8 dense star-forming regions within 1kpc. This survey will image multiple fields in each target cluster with the 11, 19, 31 and 37 micron bands, including an estimated 100 young stellar objects (YSO) with bright mid-IR emission. The results will fill in YSO information for the cluster centers where previous studies based on Spitzer, WISE, and IRAS were saturated and/or suffered from source confusion. In addition, these observations will help fill the 10-40 micron gap in the spectral energy distributions of YSOs in these fields, and will help characterize the spatial extent of the 31 micron and 37micron emission. FORCAST’s high spatial resolution will be an improvement by a factor of two over the Spitzer 24 micron images. The proposed survey will provide better statistics on bright young cluster stars which will help test current theories of clustered star formation: Turbulent Core Collapse and Competitive Accretion. Specifically, the data will improve our knowledge of the protostellar luminosity and temperature distributions in the dense regions of forming clusters, which constrain these models (Offner and Mckee 2011; Myers 2011). In addition, the extent of the 31 and 37 micron emission (unresolved compared to 5-10") will provide direct information on Competitive Accretion.
Proposal ID: 02_0072
Principal Investigator: Karin Sandstrom (Max-Planck-Institut fur Astronom)
Title: Spectrally Resolved [CII] Emission in M31: The Origin of [CII] from Metal-Rich Star-Forming Galaxies
Abstract: Understanding the contribution of the various interstellar medium phases to the [CII] 158 micron line is crucial for using it as a diagnostic of ISM conditions or as a tracer of star formation in galaxies at a variety of redshifts. Our neighboring galaxy M31 provides a uniquely powerful target for such a study due to the wide array of ancillary data we have assembled to study its ISM and stellar populations. We propose to use the GREAT instrument on SOFIA to observe the velocity-resolved emission of the [CII] line in several regions along the major axis of the galaxy. With these GREAT observations and our new high velocity resolution HI and CO maps of M31, we will compare the velocity components from the three tracers to determine how much of the [CII] arises from cold atomic gas and the photodissociation regions on the borders of molecular clouds. This key information about the origin of [CII], along with detailed stellar population studies from Hubble, will let us perform a unique study of ISM heating and cooling in the nearest metal-rich, star-forming galaxy.
Proposal ID: 02_0074
Principal Investigator: Jonathan Tan (University of Florida)
Title: Peering to the Heart of Massive Star Birth - III. Surveying Across Evolution and Environment
Abstract: We propose to utilize the unique capabilities of SOFIA-FORCAST to perform a 30-40 micron imaging survey of massive protostars, building upon our Basic Science results on G35.20-0.74 (hereafter G35.2) and our approved Cycle 1 observations of several more sources. We have demonstrated theoretically and observationally that 30-40 micron observations are crucial for defining the spectral energy distribution of massive protostars and thus the bolometric flux directed towards us. The 40 micron peak brightness is typically very close to the actual protostar’s position, while at shorter wavelengths this is often not the case due to re-radiation via outflow cavities. SOFIA’s relatively high angular resolution at 30-40 microns, i.e. ~3" compared to ~6" of Herschel at 70 microns, is thus important for disentangling massive star formation activity, especially that occurring in crowded regions. With G35.2 we have also demonstrated SOFIA’s ability to deliver high contrast imaging revealing fainter extended emission from the protostellar envelope that is impractical to observe from the ground at 10-20 microns. Combined with sophisticated radiative transfer modeling, analysis of this emission constrains the geometry of the outflow cavities, allowing more reliable measurement of the true bolometric luminosity and thus protostellar mass. Our goal now is to apply these techniques to a much larger sample of protostars, spanning a wider range of evolutionary and environmental states, from relatively isolated sources in Infrared Dark Clouds, to less extincted sources with compact (often jet-like) radio emission, to ultra-compact HII regions (where radio emission extends beyond MIR emission), to sources in crowded regions. A typical observation will take ~60 minutes and the ~40 targeted fields of view will yield >~50 protostars: enough to begin to provide statistically significant samples in these different evolutionary and environmental states.
Proposal ID: 02_0076
Principal Investigator: Anthony Remijan (NRAO)
Title: Observational Evidence of Iron Hydride in the ISM - Search for FeH in the Supernova Remnant IC 443
Abstract: The most abundant molecular species in astronomical environments are light hydrides - of course with the bulk of the abundance in H2. The presence of these species are enigmatic - the formation route to many light hydrides are highly endothermic and many of these species are not thermodynamically stable with respect to collisions with common ISM species or strong UV radiation. Yet, numerous hydrides have been detected in the ISM (CH,OH,NH,FH,SH,ClH,SiH).The detection of all of these species implies significantly energetic conditions/processing in interstellar environments. This is particularly true of SiH and SH, the two least energetically favorable hydrides detected. SOFIA provides the unique observing platform to continue the search for metal hydrides in astronomical environments. With a cosmic abudance comparable to sulfur, iron is one of the highest mass atomic species that could react with hydrogen to form iron hydride (FeH). The FeH radical has been the focus of many spectroscopic studies due to the complexity of its electronic, vibrational and rotational structure. It is also an important species for astronomical searches in determining the formation properties of metal hydrides in astronomical environment. For example, it is present in the atmosphere of the sun and has been detected in M-dwarf stars (Wende et al 2010). This proposal will search for the cosmic origins of FeH by targeting an extremently energetic Fe rich environment interacting with ambient molecular H gas - the Supernova Remnant IC 443. Given the high sensitivity and frequency range available to the GREAT instrument, SOFIA is the only astronomical facility in the world that can conduct this experiment.
Proposal ID: 02_0079
Principal Investigator: Klaus Pontoppidan (STScI)
Title: Are Herbig Ae disks really depleted of water vapor?
Abstract: Spitzer discovered that protoplanetary disks around low-mass stars generally exhibit strong mid- infrared emission from warm water vapor and other molecules. The emission originates in the planet-forming region around 1 AU. Conversely, disks around the more massive, hot and luminous Herbig Ae stars do not show detectable water emission. There is still no agreed-upon explanation for this very strong observation. We propose to use EXES to conduct a sensitive search for warm water vapor in a sample of protoplanetary disks around Herbig Ae stars (a few solar masses). The sample is chosen from a database of high quality Spitzer spectra to contain disks that show hints of water emission beyond 20 micron. The observations will firmly demonstrate whether there really is a deficit of water in the the surfaces of Herbig Ae disks, or whether more mundane radiative transfer effects caused line fluxes to be suppressed just enough that they dropped below the Spitzer detection threshold. If the former holds, it is possible that the bulk disk chemistry around Herbig stars is different from that of disks around low-mass stars, potentially leading to different compositions and demographics of the planetary systems formed by the disks.
Proposal ID: 02_0084
Principal Investigator: Claudia Dreyer (Deutsches Zentrum fur Luft- und Raumfahrt eV, IfP)
Title: Transit spectrophotometry of the Super-Earth exoplanet GJ 1214b with FLIPO
Abstract: We propose to use FLIPO on SOFIA to comprehensively analyze the atmospheric composition of the first planet in the super-Earth range to be characterized: the possible water-world GJ 1214b. These observations will allow us to determine the chemical composition of the atmosphere. Our constraints on these aspects of the planetary atmosphere will be achieved through spectrophotometric transmission observations during transits in 2 optical and 2 infrared channels - the 1.90 micron `Paschen alpha cont.’ and 3.05 micron `water ice’ - that are not observable from the ground. Furthermore HIPO and FLITECAM (in the FLIPO configuration) are the only instruments available for simultaneous optical and IR observations: SOFIA has unique capability to provide quasi space-based photometry enabling us to answer the state-of the-art scientific question whether GJ 1214b is a `water-world’ or a small Neptune-like gas-giant. Our observations will pave the way for future observations of a wide range of exoplanet atmospheres with FLIPO on SOFIA.
Proposal ID: 02_0085
Principal Investigator: Lizette Guzman-Ramirez (European Southern Observatory - Chile)
Title: The Mixed-Chemistry Problem in Planetary Nebulae
Abstract: Planetary nebulae (PNe) represent the last stage of evolution of intermediate mass stars (0.8 to 8M_sun) and hence by their very nature are fundamental to galactic evolution. The massive envelopes ejected during their earlier evolution (AGB phase) are an important source of recycled material in the form of dust and molecular gas into the interstellar medium. A small fraction of PNe show both O- and C-rich features and are therefore classified as mixed-chemistry objects. The origin of their mixed-chemistry is still uncertain. Our chemical models show that the PAHs may form in irradiated dense tori, and HST images confirm the presence of such tori in some of the objects. Using the VISIR/VLT, we spatially resolved the precise location of the PAHs. We find a dense dusty structures in all of the objects observed. The ionised [SIV] material is located inside the dusty tori, while the PAHs are present at the outer edges of these tori. This confirms that the PAHs formation is due to the photodissociation of CO. In the Galactic Disk, very few PNe have shown to harbour these mixed-chemistry phenomenon. We propose to observe the tori a sample of bipolar PNe from the Galactic Disk that harbour a close binary system inside them. The chemical models show that the formation of long C-chain molecules is possible to occur in O-rich environments, the formation of these C-rich molecules require a very dense region (Av~4). To test these theory we propose to observe the very dense tori of these Galactic Disk PNe and compare these sample with the already observed sample of PNe in the Galactic Bulge (Guzman-Ramirez, et al., 2011;Guzman-Ramirez, et al., 2013, submitted).
Proposal ID: 02_0087
Principal Investigator: Stephan Schlemmer (Universitaet zu Koeln)
Title: Observing para-H2D+ absorption towards Serpens SMM1
Abstract: We propose to observe the the ground-state rotational line of para-H2D+ at 1370 GHz (? = 218?m) with SOFIA/GREAT. The line is predicted to be detectable in absorption towards the luminous low-mass Class 0 protostar Serpens SMM1. This northern source consists of a warm, edge-on dust disk with a strong FIR continuum emission (280 Jy at 218 ? m) surrounded by a massive, cool envelope. According to our estimates the para H2D+ line is optically thick (? = 1) and will absorb about 60% of the continuum emission. The expected line absorption signal is at least 0.2 K in TA?, but only ?1 km/s wide. Even with SOFIA/GREAT the proposed project is challenging and needs deep integration, but it also renders possible an unambiguos detection of para-H2D+. As the object is particularly well studied in molecular lines and dust continuum, the proposed observations will allow us to test our understanding of the deuterium chemistry.
Proposal ID: 02_0089
Principal Investigator: Thomas G. Muller (Max-Planck-Institut fur extraterrestrische Physik)
Title: Stellar occultations by large Transneptunian Objects (dwarf planets candidates)
Abstract: Occultations of stars by Transneptunian Objects (TNOs) had never been observed (except for Pluto-Charon system), but in slightly more than three years, 12 such occultations have been detected. This has been a breakthrough. Stellar occultations allow us to derive accurate diameters, shapes and albedos of TNOs. Besides, the presence of atmospheres can be determined and the orbits can be refined. We request two attempts to observe occultations with SOFIA / HIPO during Cycle 2. Occultations by TNOs are brief and the uncertainties in timing require only around 0.33 hrs of observations per alert. The predictions only become accurate enough around 1 or 2 weeks prior to the occultation. This is why a target of opportunity proposal with SOFIA / HIPO is requested.
Proposal ID: 02_0090
Principal Investigator: Els Peeters (SETI Institute)
Title: Evaporation flows driven by early B stars.
Abstract: Young massive OB stars significantly influence their environment as their far-UV photons (6 eV < E < 13.6 eV) dominate the physics and chemistry of the surrounding gas, creating PhotoDissociation Regions (PDRs). The incident FUV field heats and photo-dissociates the PDR and may create evaporation flows of the PDR surfaces. These photo-evaporated flows are fundamental to understanding proplyds, pillars, and the evolution of molecular clouds and hence may greatly influence the star and planet formation process. As the far-UV luminosity of the galaxy is dominated by later type B stars rather than O stars, understanding the interaction of B stars with nearby molecular clouds is key. However, for the majority of the PDRs -- those associated with lower mass B stars -- the photo-evaporation process and its relation with star formation are not well studied. Here, we propose a velocity-resolved study of the [CII] line at 158 micron with the GREAT spectrometer on board of SOFIA to study the dynamical interaction of the B2V star HD 39703 and the B0.5IVe star gamma Cas with the molecular cloud they illuminate. These regions are well-studied over a wide-wavelength range and have been observed by Spitzer/IRS in spectral mapping and Herschel/PACS in both photometry and line-mapping (cooling lines, CO). The goal of this combined SOFIA/Herschel/Spitzer study is to address the kinematic characteristics of the interaction of these two stars with the molecular cloud, determine the mass loss rate, and assess their role in triggering star formation in the PDR. In this way, we can assess the role of evaporation flows driven by early B stars in the evolution of molecular clouds.
Proposal ID: 02_0094
Principal Investigator: Michael Person (Massachusetts Institute of Technology)
Title: Atmospheric Change on Pluto
Abstract: We propose to use SOFIA with HIPO and FLITECAM (FLIPO) to measure the parameters of Pluto’s atmosphere (temperature, pressure, possible particulate haze) by observing a stellar occultation by Pluto on 15 November 2014. Due to its highly elliptical orbit and seasonally variable obliquity, Pluto’s atmosphere is predicted to condense onto its surface within the next ~10 years and possibly within the next few years and thus frequent observations are critical. Detection of the occultation central flash will allow measurement of the structure of Pluto’s lower atmosphere and atmospheric oblateness. We will use FLIPO to measure the refracted starlight contemporaneously at visible and infrared wavelengths; this approach is needed to differentiate between two competing explanations for the deficiency in the observed light refracted from Pluto’s lower atmosphere (strong thermal gradients versus variable particulate extinction). Only an airborne platform such as SOFIA has the flexibility to place a large telescope in the center of the shadow path of this brief event while at the same time nearly eliminating the possibility of missing time-critical observations due to unfortunate weather systems. Occultation predictions will be updated throughout the period preceding the observations with the goal of achieving sufficient prediction accuracy at the event time to place SOFIA directly in the path of Pluto’s central flash. This SOFIA observation will be combined with our ongoing ground-based observing program whose goal is to measure the temporal variability of Pluto’s atmosphere in response to its changing seasonal obliquity (and resulting ice migration) and recession from the sun. For the NASA New Horizons mission to Pluto and the Kuiper Belt, this Pluto occultation event represents the last chance, prior to the spacecraft closest approach to the Pluto/Charon system (July 2015), to provide input to the mission for encounter planning, as well as context and supporting atmospheric information.
Proposal ID: 02_0095
Principal Investigator: Sarah Ragan (Max-Planck-Institut fur Astronomie, Heidelberg)
Title: FIFI-LS Observations of Coolants in IRDCs
Abstract: Infrared dark clouds (IRDCs) contain the earliest phases of high-mass star formation. While the study of their coldest, densest regions has advanced enormously over the past decade with molecular line studies and the advent of Herschel, little has been done to observe their warm gas content. The fine structure lines of neutral oxygen ([OI]) and singly ionized carbon ([CII]) are the most important tracers of the warm gas in molecular clouds and provide strong constraints on the energy input and output of the cloud. We propose to map a small sample of clouds which have a variety of stellar content. By probing regions of massive star formation in particular, we can better discern the relative importance of UV ionization from internal sources and that from the interstellar radiation field. Our goal is to provide fundamental constraints to ISM models which are crucial to understand the regulation of star formation throughout different environments in the Galaxy.
Proposal ID: 02_0096
Principal Investigator: Bruce McCollum (Catholic University of America)
Title: Exploring the Far-infrared SED of the First Known Stellar Merger Remnant
Abstract: The 2008 merger of two stars in the system V1309 Sco offers an unprecedented opportunity to obtain multiwavelength data of a merger remnant before it has evolved into a normal-looking star. A large body of theoretical work in the past few decades has shown that stellar mergers are astrophysically important influences on dense stellar environments. Until this object’s outburst was proven to have been a merger, no events were known which were definitely mergers, so a lack of data on any merger during and soon after the event has critically impeded our understanding of the merger process and its ejecta. Recent near-IR spectra show that V1309 Sco has developed a dusty, chemically complex circumstellar environment which may still be evolving. Dust modeling predicts a far-IR tail which should be observable by FIFI-LS. It is important to obtain far-IR data in order to create a full SED of the merger remnant as a basis for future modeling and to search for emission lines which may be present and which can reveal important information about the processes occurring in the merger ejecta.
Proposal ID: 02_0100
Principal Investigator: Peter Garnavich (University of Notre Dame)
Title: Mind the Gap: Filling the Holes in IR Spectra of Type Ia Supernovae
Abstract: Type Ia supernovae are essential tools for cosmology, but to tightly constrain dark energy properties their systematic uncertainties must be controlled. The near-IR appears to be an excellent spectral region for supernova studies because at these wavelengths Type Ia explosions are essentially standard candles and dust extinction is low. One difficulty is that the Earth’s atmosphere blocks sections of the 1 to 2 micron spectra range so parts of the spectrum are not well-observed in nearby events while they are included in the photometric measurements at higher redshifts. This creates an uncertainty in IR “k-corrections" for cosmologically interesting supernovae. We propose to fill in these gaps by observing two nearby Type Ia with SOFIA as targets of opportunity.
Proposal ID: 02_0101
Principal Investigator: Nathan Smith (University of Arizona)
Title: Constraining the Mass in Cool Dust Shells Around Massive Stars
Abstract: We propose to observe a sample of circumstellar shells around hot, massive stars in order to estimate their ejected mass and to thereby help constrain the importance of eruptive mass loss in post-main sequence stellar evolution. Very few examples currently exist with accurate determinations of the mass lost in eruptive ejections, and access to mid-IR and far-IR wavelengths is critical because of the relatively cool dust temperatures in the extended fossil remnant shells. Three of our targets are confirmed or candidate luminous blue variables (LBVs), which are hot stars in a post-main sequence exhibiting extreme mass loss events. Our fourth target, RY Scuti, is a massive binary with a comparable mass loss history, for which we seek to combine FORCAST imaging with FORCAST Grism observations to assess the mineralogy of its dust as well as determine the extent to which bright emission lines such as its previously observed [Ne II] 12.8 micron emission may affect the images.
Proposal ID: 02_0102
Principal Investigator: Friedrich Wyrowski (Max-Planck-Institut fur Radioastronomie)
Title: Probing high-J CO through the evolution of high-mass star forming clumps
Abstract: We propose to observe with SOFIA/GREAT a new representative sample of massive protostars taken from the ATLASGAL submm dust continuum survey that covers a large range of evolutionary stages. Adding to our available low- to mid-J data observations of high-J CO emission will reveal the warm CO components probing the inner heated envelopes (and their photon-dominated regions) and outflows (and their shocks). With additional modeling of the envelopes and the observed line profiles, we will be able to separate the contributions of the different components. The size of the sample will allow to search for evolution on a statistical basis. Our sample comprises sources which span the age and mass ranges adequate to represent the protostellar precursors of OB clusters, from infrared-quite objects to ultracompact HII regions.
Proposal ID: 02_0104
Principal Investigator: Adwin Boogert (California Institute of Technology)
Title: Tracing Circumstellar Environments with High Resolution Spectroscopy of Methane
Abstract: Unique high spectral resolution ground-based observations have shown that the ro-vibrational transitions of gas phase CH4 are a powerful diagnostic of the complex dynamics and chemistry in environments of star formation (Boogert et al. 2004, Knez et al. 2009). Contrary to the widely present CO, CH4 traces highly selective regions in the protostellar environment. The massive YSO NGC7538 IRS9, for example, shows P-Cygni line profiles, from an expanding 70 AU shell where ices have evaporated and a surrounding envelope with a low gas phase CH4 abundance as a result of freeze-out. CH4 is notably absent in the high velocity outflow seen in CO, possibly due to destruction in shocks. Furthermore, at moderately high temperatures and very high densities, strong CH4 abundance enhancements are expected (Fischer-Tropsch conversion of CO), tracing dense clumps (proto-planets?) in the young star’s vicinity. Finally, CH4 is highly relevant in astrobiology as a starting point of complex molecule formation. Unfortunately, observations of both the 3.3 um stretching and 7.7 um bending modes are severely hampered by the Earth’s atmosphere. Only three YSOs, all with exceptionally high heliocentric velocities (~60 km/s) were detected in gas phase CH4. With SOFIA/EXES it will finally be possible to increase the sample diversity, as smaller Doppler velocities (~15 km/s) are sufficient at altitudes of 45,000 feet. Here, we conservatively selected two massive, very bright (>150 Jy) YSOs, because the performance of SOFIA/EXES still needs to be proven. In combination with published ground-based spectra, these observations would be used to constrain the CH4 excitation, and thus its origin (NGC7538 IRS1). Also a more evolved source, never observed in CH4 was selected (MonR2 IRS3). The results would direct CH4 observations of larger samples in future observing cycles.
Proposal ID: 02_0106
Principal Investigator: Tracy Huard (University of Maryland)
Title: Resolving Protostars in the Serpens South Protocluster
Abstract: The Spitzer Space Telescope revealed a new young cluster, known as Serpens South, located in the Serpens-Aquila Rift. With a high ratio of protostars to young stellar objects, Serpens South is among the youngest known clusters. Present in the cluster core are at least two groups of protostars that are blended or confused in Spitzer MIPS observations; some of these protostars may share a common protostellar envelope. We propose FORCAST observations of the cluster core, taking advantage of the higher angular resolution to properly derive mid-infrared fluxes. With these fluxes, their spectral energy distributions may be characterized, which will provide constraints on their luminosities and physical structures. If indeed some of these protostars share envelopes, their relative luminosities may be suggestive of the winners and losers in the competition for matter from the same reservoir.
Proposal ID: 02_0108
Principal Investigator: Karl Menten (Max-Planck-Institut fur Radioastronomie)
Title: Far-Infrared Spectroscopy of OH in Three Prototypical Circumstellar Envelopes
Abstract: The hydroxyl radical (OH) exists under a large variety of conditions, thanks to several chemical pathways leading to its production. Photodissociation of water is one of them, making OH an important tracer for the outer winds of circumstellar envelopes (CSEs), but owing to shocks it is also formed in the inner regions of the outflows from some supergiants and protoplanetary nebulae. The non-LTE excitation of OH, resulting from a complex cycle starting with 35 micron absorption from the 2Pi3/2 ground state to the 2Pi1/2 state, leads to maser action, most strongly in the 1665 and 1667 ground state line. Unlike OH masers around UCHIIRs, hyperfine split radio lines from rotationally excited states have almost never been seen toward evolved stars. FIR observations are thus the only means to obtain information about the thermal OH emission from CSEs. The proposed observations of the OH ground state line will complement radio data and FIR data from HIFI and allow us to model the excitation of OH.
Proposal ID: 02_0113
Principal Investigator: James De Buizer (SOFIA - Universities Space Research Association)
Title: Revealing the Embedded Structures and Sources within Giant HII Regions
Abstract: Unlike low mass star formation, relatively little is known about massive star formation. Furthermore, most studies concentrate on the processes of isolated star formation while little is known about clustered star formation, despite the fact that the vast majority of stars are formed within clusters. Giant HII regions harbor young OB clusters, and as such are fantastic laboratories for the study of massive star formation as well as clustered star formation. However, the great majority of these GHII regions are optically obscured and far away, requiring them to be studied in the MIR/FIR with adequate spatial resolution. SOFIA 24 and 37um imaging with approximately 3 arcsecond resolution well-suited for revealing the embedded structures and sources within these regions. These SOFIA observations will be combined with data taken at other wavelengths to quantify the detailed physical properties within GHII regions on an individually and as a population. The observations will also expose the areas of the youngest stages of massive star formation within the GHII regions and allow for the confirmation or confrontation of the recently proposed evolutionary sequence of GHII regions. This proposal is designed to be a pilot study (given the limited time available during Cycle 1 & 2), which will later be expanded to a survey that will catalog all of the known GHII regions at the highest spatial resolutions yet achievable at IR wavelengths greater than 25um. Such a catalog is expected to be an invaluable tool for the SOFIA community for follow-up spectral imaging and polarimetric imaging, as well as targeted MIR/FIR spectroscopy of individual sources within these regions.
Proposal ID: 02_0114
Principal Investigator: Karsten Schindler (Deutsches SOFIA Institut)
Title: Spectroscopy of JVI Himalia for detection and characterization of the 3 um water band
Abstract: We aim at securely detecting and characterizing the presence of the 3um band for the first time in the reflectance spectrum of a Jovian irregular satellite. Features in the 3um band can unambiguously reveal water ice or past aqueous alteration of the surface material that lead to bound water molecules and hydroxyl groups in minerals. Water ice and hydrated minerals are ubiquitous in the Jovian system and have been found on Europa, Ganymede, Callisto and the inner regular satellite JV Amalthea. In contrast to these neighboring satellites and to two irregular satellites that have been studied at Saturn and Neptune, a detection of water (previously or currently present) on a Jovian irregular satellite has not yet been succeeded due to constraints of ground-based observatories. No dedicated spacecraft mission to the Jovian system has allowed to study them close-up. Their very low albedos and small diameters only allow ground-based spectroscopy up to 2.5um for very few objects. The strong telluric absorption band of the atmosphere between 2.55-2.85um and the increasing IR-background beyond 2.85um makes ground-based spectroscopy for these very faint objects impossible. SOFIA has the unique capability to overcome these limits. Flitecam provides enough sensitivity to conduct spectroscopic investigations between 2.6-3.5um of the largest object of the Jovian irregular satellite population, JVI Himalia. Supplementary high quality spectral data from 0.65-2.55um has already been acquired by Schindler and Reddy using SpeX on NASA IRTF. Three indicators strongly suggest the presence of the 3um band: A shallow absorption feature around 1.1um attributed to magnetite, a weak feature around 0.7 um attributed to phyllosillicates and an average heliocentric distance of 5.2AU where water ice is thought to be stable throughout the history of the Solar System. The results of this study will greatly contribute to understand the origin and history of these objects.
Proposal ID: 02_0115
Principal Investigator: Helmut Wiesemeyer (Max-Planck-Institut fur Radioastronomie)
Title: Exploratory search for a new, strong HCN laser in two carbon stars
Abstract: When asymptotic giant branch (AGB) stars reach the third dredge-up phase, their C/O ratio exceeds unity and they become carbon stars. SiO masers, a valuable tool to investigate the atmospheres of AGB stars, then fade away by up to two orders of magnitudes. However, non-equilibrium chemistry produces a large HCN abundance in a zone that extends from the stellar photosphere to a few stellar radii, similar to the region where SiO mases form in oxygen-rich AGB stars. Chemically pumped like their laboratory equivalents, cosmic HCN lasers, of which two were discovered a decade ago, provide a suitable surrogate for SiO masers to study the atmospheres of carbon stars. The strongest laser lines originate from levels of similar total, but different bending energy that are weakly coupled by Coriolis interaction. This exploratory project searches for such a far-infrared laser at 1421 GHz toward the two prototypical carbon stars, IRC+10216 and CIT 6, aiming at an increase of the inventory of Coriolis coupled HCN lasers for further studies of the dynamics in the atmospheres of carbon stars. In parallel, we tune to a similar HC^15N laser at 1815 GHz.