SOFIA Cycle 3 Programs in Do If Time Category

Proposal ID: 03_0008

Principal Investigator: James De Buizer (SOFIA - USRA)

Title: Revealing the Embedded Structures and Sources within Giant HII Regions: The Northern Hemisphere Sample

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 the most active areas of OB star formation in the Galaxy, and as such are fantastic laboratories for the study of massive star formation as well as clustered star formation. However, 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 19.7 and 37.1um imaging with approximately 3 arcsecond resolution well-suited for revealing the embedded structures and sources within these regions. These SOFIA observations will be combined with data taken at other wavelengths to quantify the detailed physical properties within GHII regions individually and as a population. The observations will also expose the areas of the youngest stages of massive star formation within the GHII regions and allow for the confirmation or confrontation of the recently proposed evolutionary sequence of GHII regions. This proposal is designed to catalog all of the known GHII regions at the highest spatial resolutions yet achievable at IR wavelengths greater than 20um. 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: 03_0009

Principal Investigator: James De Buizer (SOFIA - USRA)

Title: Revealing the Embedded Structures and Sources within Giant HII Regions: The Southern Hemisphere Sample

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 the most active areas of OB star formation in the Galaxy, and as such are fantastic laboratories for the study of massive star formation as well as clustered star formation. However, 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 19.7 and 37.1um imaging with approximately 3 arcsecond resolution well-suited for revealing the embedded structures and sources within these regions. These SOFIA observations will be combined with data taken at other wavelengths to quantify the detailed physical properties within GHII regions individually and as a population. The observations will also expose the areas of the youngest stages of massive star formation within the GHII regions and allow for the confirmation or confrontation of the recently proposed evolutionary sequence of GHII regions. This proposal is designed to catalog all of the known GHII regions at the highest spatial resolutions yet achievable at IR wavelengths greater than 20um. 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: 03_0013

Principal Investigator: Wolfgang Brandner (Max-Planck-Institut fur Astronomie Heidelberg)

Title: Disentangling the complex ISM structure of the Galactic starburst W49

Abstract: During their early evolution massive stars ionize their natal molecular cloud and create expanding HII regions as well as surrounding Photo Dissociation Regions (PDR). The physical and chemical details of the interplay between the HII region, its PDR and the molecular cloud, and their evolution with time are far from clear. A better understanding is vital to determine the feedback of massive stars on the ISM, and the triggering of the next generation of stars. We propose to study the evolution of the complex interplay between the different phases of the ISM associated with one of the most luminous Giant HII region and Giant Molecular Cloud complexes in our Galaxy: W49. We will use SOFIA/FORCAST observations at 31.5 and 37.1 micron to trace the distribution and temperature of hot dust across the region. Supporting multi-wavelength data will provide a full view of all ISM phases of W49. Combined with our stellar population studies, which provide stellar ages, spectral types, and luminosities, and hence energy input (and its duration) into the ISM, evolutionary models for HII regions and PDRs will be calibrated. As the most luminous HII region complex in our Galaxy, W49 is an excellent place to study the ISM components, and serves as a template for more massive, unresolved star forming regions in other galaxies. We will test and validate models, which previously have been applied to extragalactic starburst regions, taking advantage of the uniquely fine and detailed spatial resolution offered by SOFIA at 31.5 and 37.1 micron.


Proposal ID: 03_0025

Principal Investigator: Alexander Zernickel (I. Physikalisches Institut der Universitaet Koeln)

Title: Observations of [CII] in the filamentary structures of the massive star-forming region NGC 6334

Abstract: We propose to observe a subfilament in the massive star-forming region NGC 6334 in [CII] and [OI] with GREAT. Because massive star formation depends crucially on the accretion process, our scientific goal is to study the gas mass flow in the filament and ambient gas and its kinematic structure. While previous observations of dense gas allowed us to study the velocity field in the main filament, only with SOFIA we are capable to use the FIR cooling lines of [CII] and [OI] to trace the lower density atomic gas as well as the CO dark gas and the transition to the dense molecular gas. The filament itself (60 pc extension) has been mapped on larger scales in an accompanying APEX observation in two isotopologues of CO, and the combination of these observations will allow us to probe the connection between the molecular and atomic gas. We expect information about the mass distribution, mass supply and pressure in the subfilaments and diffuse gas. The data will be analyzed by using well-established radiative transfer and PDR codes to derive the physical parameters.


Proposal ID: 03_0033

Principal Investigator: Joel Green (University of Texas at Austin)

Title: Shock origins in young stellar objects using resolved [O I] 63 um lines observed by GREAT

Abstract: We propose to use the unprecedented resolution of SOFIA-GREAT at 63 um to distinguish the components of the [O I] line in the protostar L1551-IRS5, to measure the wind and molecular shock. The formation of stars and planets requires a transfer of angular momentum by fast (100 km/s) winds. These winds also remove much of the circumstellar envelopes of embedded protostars, controlling the mass of the star/disk system. The interaction of the wind with the envelope is an essential aspect of star formation, but winds are only observed indirectly; the gas swept up in the wind forms a molecular outflow with velocities of a few to 10s of km/s. Direct observation of winds from embedded protostars is difficult because the atomic lines that trace the particle flux are typically emitted at optical/UV wavelengths, where they are attenuated by the enveloping dust. The [O I] 63 um fine-structure emission line should be an excellent tracer of the wind flux. Neutral oxygen should be produced in the shocked wind and the [O I] line at 63 um would provide a direct measure of the mass loss rate in the wind. However, our Herschel studies of embedded protostars show that the [O I] line, while readily detected, is weaker than expected, casting doubt on its use to measure the mass loss rate in the wind. In addition, there are other possible causes of [O I] emission, such as photodissociation or shocks into the molecular gas, which could be contributing to the observed [O I] lines, which Herschel barely resolves. While the Herschel data hint at wide lines, the spectral resolution was inadequate to rule out a significant contribution from narrow (< 10 km/s) components, which would not arise in the wind. We propose to use SOFIA-GREAT to answer the question: is there a narrow velocity component in the [O I] line? We propose to use the high spectral resolution of GREAT to measure the line profiles toward one of the strongest [O I] emitters in our sample, L1551-IRS5.


Proposal ID: 03_0040

Principal Investigator: Fabrice Herpin (Laboratoire d’Astrophysique de Bordeaux)

Title: Water in Massive protostellar objects: first detection of THz water maser and water inner abundance.

Abstract: The formation massive stars is still not well understood. Despite numerous water line observations with Herschel telescope, over a broad range of energies, in most of the observed sources the WISH-KP (Water In Star-forming regions with Herschel, Co-PI: F. Herpin) observations were not able to trace the emission from the hot core. Moreover, water maser model predict that several THz water maser should be detectable in these objects. We aim to detect for the first time the THz maser lines o-H2O 8(2,7)- 7(3,4) at 1296.41106 GHz and p-H2O 7(2,6)- 6(3,3) at 1440.78167 GHz as predicted by the model. We propose two sources for a northern flight as first priority and two other sources for a possible southern flight. This will 1) constrain the maser theory, 2) constrain the physical conditions and water abundance in the inner layers of the prostellar environnment. In addition, we will use the p-H2O 3(3,1)- 4(0,4) thermal line at 1893.68651 GHz (L2 channel) in order to probe the physical conditions and water abundance in the inner layers of the prostellar objects where HIFI-Herschel has partially failed.


Proposal ID: 03_0056

Principal Investigator: Randolf Klein (Universities Space Research Association)

Title: The Early Evolution of Very Massive Star-Forming Cores

Abstract: Context- Massive stars strongly affect their surroundings and even their host galaxy due to their high energy input into the interstellar medium (ISM) throughout their lifetimes. But how do massive stars form from the ISM? Despite all the progress in the area of star formation, the answer to this important question is still unclear. Aims - We want to tackle the above question by looking at the earliest phases of massive star formation (MSF). A great step forward is made when the initial conditions for massive star formation are better understood. Building on our NASA-supported study of early massive cores, we want to study the most massive cores of that sample in the mid-infrared (MIR), because the Spitzer maps of these cores are very often saturated. Methods - We propose to obtain FORCAST images in four broad band filters from 11 ?m to 37 ?m of the selected very massive cores. Anticipated results - The MIR images and color temperature maps derived from them will tell us where the heating sources are in the very massive cores detected in the (sub-)millimeter continuum. By combining the FORCAST data with near infrared data (2MASS), far infrared data (Herschel) and the millimeter data, we can characterize the massive cores and infer an evolutionary stage and so trace the early evolution of massive protostars and their surroundings. Non-detections by FORCAST at the locations of the massive cores would be very interesting as that would indicate a very early stage of MSF possibly a pre-stellar massive core to further study the initial conditions of massive star formation.


Proposal ID: 03_0077

Principal Investigator: Juan-Pablo Perez-Beaupuits (Max-Planck-Institut fur Radioastronomie Bonn)

Title: Unveiling the dark molecular gas and ionized gas in M17SW with [O I] and [N II] maps.

Abstract: The SOFIA/GREAT velocity-resolved map of the [C II] 158 um line in M17SW shows broader spectral lines (covering the range from 0 to 40 km/s) than the low-, mid- and high-J CO and [C I] lines obtained with ground-based telescopes. Channel maps showed that the spatial distribution of [C II] is not associated to that of the CO and [C I] emissions at the lower (<14 km/s) and higher (>24 km/s) velocity channels. This means that more than 60% of the [C II] emission in the region mapped is not associated with the gas traced by the CO and [C I] lines. The not associated [C II] emission may not emerge from clump surfaces nor the interclump medium, but it may correspond to material being ablated by hard enough (>11.26 eV) UV photons. In order to understand the origin of the [C II] emission, we proposed complementary maps of the velocity-resolved [O I] 63 um and [N II] 205 um fine-structure lines, as tracers of dark molecular gas and ionized gas, respectively. When considering the source elevation (38 deg.) and water vapour content (~20 um) usually seen at Palmdale, this project would need ~3.4 hours. However, since M17SW is a southern source, its higher elevation (~60 deg.) and the lower water vapour content (~10 um) would allow us to complete this project in only ~2.2 hours, if observed from Christchurch, NZ.


Proposal ID: 03_0079

Principal Investigator: Kathleen Kraemer (Boston College)

Title: Fullerene Emission from Crystalline Silicate Sources: A FORCAST Investigation

Abstract: The infrared spectra of evolved stars are typically dominated by features from either carbon-rich grains and molecules or by oxygen-rich grains and molecules. Recently, the very large molecule buckminsterfullerene, C_60, has been detected, primarily around carbon-rich evolved objects such as post-AGB stars and planetary nebulae, but also from a small number of oxygen-rich sources. Thus, the physical conditions necessary to produce this molecule are not yet well understood. Our goal is to better constrain the physical conditions that are needed to for fullerene production and detection around evolved stars. In particular, we will examine a sample of 21 evolved stars in the Milky Way that are known to have crystalline silicate features in their infrared spectra, as these are the type of oxygen-rich source that fullerene have been detected in. We request 3.65 hours with the FORCAST grism on SOFIA to obtain 17.6-27.7 micron spectra of our targets, which covers the 18.9 micron fullerene emission feature.


Proposal ID: 03_0102

Principal Investigator: Timea Csengeri (Max-Planck-Institut fur Radioastronomie Bonn)

Title: The origin of ridges: signatures of shocks

Abstract: Supersonic flows of dense gas are witnessed at the sites of massive filaments hosting precursors of OB type stars. So far only few observational examples could be found providing evidence for low-velocity shocks, which would be the proof that indeed these flows collide and build up massive structures. Supersonic MHD models predict the OI line to be the main cooling agent in high density (n>10^5 cm-3), low-velocity (v < 20 km/s) shocks. The SOFIA/GREAT receiver provides the first opportunity to spectrally resolve the line profile of the 63 micron OI line, which would provide the first direct evidence for these shocks. We therefore propose to map this line, together with the CII line towards the best potential sites of converging flows. The proposed observations, together with ancillary Herschel data, allow a full characterization of the physical conditions to disentangle between the broad component originating from outflows, the narrow component from low-velocity shocks, while the intensity of the line compared to PDR model reveals the possible contribution to the observed of the emission. Altogether this comprehensive approach will allow for the first time to directly probe this process which may play a key role in building up massive structures.


Proposal ID: 03_0112

Principal Investigator: Silvia Leurini (Max Planck Institut fuer Radioastronomy)

Title: Far-infrared line coolants in massive star-forming regions

Abstract: The lines of [OI] and [CII] are powefulr tracers of different environments. In photo-dissociation regions (PDRs) their line ratio strongly depends on density; in molecular outflows from low-mass young stellar objects the luminosity of the [OI] line at 63 micron is directly proportional to the rate of mass outflow from the star and it is independent on visual extinction, inclination, and geometry of the outflow. In metal-rich galaxies, [OI] and [CII] lines are among the main coolants, and being very luminous, they are potentially powerful tracers of star formation rates (SFRs) even in galaxies at high z. However, [OI] and [CII] were till now observed only with very poor spectral resolution. They can be heavily affected by absorptions from the source or from different foreground clouds, and the contribution of outflows and PDRs cannot be quantified without resolved profiles. Therefore their diagnostic value is of limited use. We propose here to exploit the unprecedented resolution of the GREAT receiver aboard SOFIA for the first spectroscopically resolved observations of [OI] and [CII] of a sample of galactic massive star-forming clumps. The sources are a flux-limited sub-sample from the ATLASGAL continuum survey of the inner Galaxy and cover a broad range of evolutionary phases. Thanks to the wealth of already collected ancillary data (in particular water, high-J CO and NH3), the proposed observations will be fundamental to calibrate [OI] and [CII] as PDR, outflow and SFR tracers in a sample of sources rapresentative of the Galactic population of massive star-forming clumps. The data will answer the following questions: Which ISM components do [OI] and [CII] trace? How does the complete (CO+H2O+[OI]+[CII]) FIR cooling budget change with bolometric luminosity? Does [OI] show prominent high-velocity emission in massive sources or is ti dominated by PDR emission?


Proposal ID: 03_0143

Principal Investigator: Will Fischer (NASA Goddard Space Flight Center)

Title: Characterizing the Youngest Known Outbursting Protostar from FORCAST Imaging

Abstract: We have identified an outbursting protostar from multi-epoch, mid-IR imaging in Orion. This object is deeply embedded and could be the youngest outbursting protostar that is known. We propose to observe this protostar and one other previously identified outburst source in Orion with FORCAST imaging at 11 - 37 microns which allow us to track the time evolution of their luminosities over a longer time baseline than is covered by our existing photometry. Additionally, FORCAST imaging will allow us to characterize the evolutionary classes of these objects. Characterization of these objects will bring insight into the processes of episodic accretion in protostars.


Proposal ID: 03_0155

Principal Investigator: David Principe (Rochester Institute of Technology)

Title: Investigating Dusty Disks in Low Mass Stars: FORCAST Imaging of the Nearby Pre-MS Binary TWA 30 A and B

Abstract: The recently discovered binary system TWA 30 consists of two of the nearest known examples of actively accreting, pre-MS star systems. Both components of TWA 30 have masses just above the brown dwarf regime and are orbited by circumstellar disks viewed nearly edge-on, with evidence for collimated stellar outflows. TWA 30A, a known X-ray source, exhibits large, variable optical/IR extinction that is evidently due to variable disk absorption. TWA 30B displays large variable infrared excess possibly indicative of a rim or warp at the inner edge of the disk. We propose to use SOFIA FORCAST to constrain disk dust structures and masses, dust grain properties and also explore mid-IR variability in these two newly discovered nearby young, very low-mass star/disk systems.

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