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1. The Mid-infrared Molecular Inventory toward Orion IRc2

Author

Sarah Nickerson, Naseem Rangwala, Sean W. J. Colgan, Curtis DeWitt, Jose S. Monzon, Xinchuan Huang, Kinsuk Acharyya, Maria N. Drozdovskaya, Ryan C. Fortenberry, Eric Herbst, and Timothy J. Lee

Subjects
Infrared astronomy, Interstellar medium, Molecular spectroscopy, Spectral line identification, Molecular physics, Astrochemistry, Astrophysics, QB460-466
Abstract

We present the first high spectral resolution mid-infrared survey in the Orion BN/KL region, covering 7.2–28.3 μ m. With SOFIA/EXES, we target the enigmatic source Orion IRc2. While this is in the most prolifically studied massive star-forming region, longer wavelengths and molecular emission lines dominated previous spectral surveys. The mid-infrared observations in this work access different components and molecular species in unprecedented detail. We unambiguously identify two new kinematic components, both chemically rich with multiple molecular absorption lines. The “blue clump” has v _LSR = −7.1 ± 0.7 km s ^−1 , and the “red clump” has 1.4 ± 0.5 km s ^−1 . While the blue and red clumps have similar temperatures and line widths, molecular species in the blue clump have higher column densities. They are both likely linked to pure rotational H _2 emission also covered by this survey. This work provides evidence for the scenario that the blue and red clumps are distinct components unrelated to the classic components in the Orion BN/KL region. Comparison to spectroscopic surveys toward other infrared targets in the region show that the blue clump is clearly extended. We analyze, compare, and present in-depth findings on the physical conditions of C _2 H _2 , ^13 CCH _2 , CH _4 , CS, H _2 O, HCN, ${{\rm{H}}}^{13}\mathrm{CN}$ , HNC, NH _3 , and SO _2 absorption lines and an H _2 emission line associated with the blue and red clumps. We also provide limited analysis of H _2 O and SiO molecular emission lines toward Orion IRc2 and the atomic forbidden transitions [Fe ii ], [S i ], [S iii ], and [Ne ii ].

Published
2023
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2. PDRs4All: A JWST Early Release Science Program on Radiative Feedback from Massive Stars

Author

Olivier Berné, Émilie Habart, Els Peeters, Alain Abergel, Edwin A. Bergin, Jeronimo Bernard-Salas, Emeric Bron, Jan Cami, Emmanuel Dartois, Asunción Fuente, Javier R. Goicoechea, Karl D. Gordon, Yoko Okada, Takashi Onaka, Massimo Robberto, Markus Röllig, Alexander G. G. M. Tielens, Sílvia Vicente, Mark G. Wolfire, Felipe Alarcón, C. Boersma, Amélie Canin, Ryan Chown, Daniel Dicken, David Languignon, Romane Le Gal, Marc W. Pound, Boris Trahin, Thomas Simmer, Ameek Sidhu, Dries Van De Putte, Sara Cuadrado, Claire Guilloteau, Alexandros Maragkoudakis, Bethany R. Schefter, Thiébaut Schirmer, Stéphanie Cazaux, Isabel Aleman, Louis Allamandola, Rebecca Auchettl, Giuseppe Antonio Baratta, Salma Bejaoui, Partha P. Bera, Goranka Bilalbegović, John H. Black, Francois Boulanger, Jordy Bouwman, Bernhard Brandl, Philippe Brechignac, Sandra Brünken, Andrew Burkhardt, Alessandra Candian, Jose Cernicharo, Marin Chabot, Shubhadip Chakraborty, Jason Champion, Sean W. J. Colgan, Ilsa R. Cooke, Audrey Coutens, Nick L. J. Cox, Karine Demyk, Jennifer Donovan Meyer, Cécile Engrand, Sacha Foschino, Pedro García-Lario, Lisseth Gavilan, Maryvonne Gerin, Marie Godard, Carl A. Gottlieb, Pierre Guillard, Antoine Gusdorf, Patrick Hartigan, Jinhua He, Eric Herbst, Liv Hornekaer, Cornelia Jäger, Eduardo Janot-Pacheco, Christine Joblin, Michael Kaufman, Francisca Kemper, Sarah Kendrew, Maria S. Kirsanova, Pamela Klaassen, Collin Knight, Sun Kwok, Álvaro Labiano, Thomas S.-Y. Lai, Timothy J. Lee, Bertrand Lefloch, Franck Le Petit, Aigen Li, Hendrik Linz, Cameron J. Mackie, Suzanne C. Madden, Joëlle Mascetti, Brett A. McGuire, Pablo Merino, Elisabetta R. Micelotta, Karl Misselt, Jon A. Morse, Giacomo Mulas, Naslim Neelamkodan, Ryou Ohsawa, Alain Omont, Roberta Paladini, Maria Elisabetta Palumbo, Amit Pathak, Yvonne J. Pendleton, Annemieke Petrignani, Thomas Pino, Elena Puga, Naseem Rangwala, Mathias Rapacioli, Alessandra Ricca, Julia Roman-Duval, Joseph Roser, Evelyne Roueff, Gaël Rouillé, Farid Salama, Dinalva A. Sales, Karin Sandstrom, Peter Sarre, Ella Sciamma-O’Brien, Kris Sellgren, Matthew J. Shannon, Sachindev S. Shenoy, David Teyssier, Richard D. Thomas, Aditya Togi, Laurent Verstraete, Adolf N. Witt, Alwyn Wootten, Nathalie Ysard, Henning Zettergren, Yong Zhang, Ziwei E. Zhang, Junfeng Zhen, Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Institut d'astrophysique spatiale (IAS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), University of Western Ontario (UWO), Carl Sagan Center, SETI Institute, University of Michigan [Ann Arbor], University of Michigan System, Analytic and Computational Research, Inc. - Earth Sciences (ACRI-ST), Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique et Atmosphères = Laboratory for Studies of Radiation and Matter in Astrophysics and Atmospheres (LERMA), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-CY Cergy Paris Université (CY), Institut des Sciences Moléculaires d'Orsay (ISMO), Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Observatorio Astronomico Nacional, Madrid, Instituto de Física Fundamental [Madrid] (IFF), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Universiteit Gent = Ghent University (UGENT), Space Telescope Science Institute (STSci), Physikalisches Institut [Köln], Universität zu Köln = University of Cologne, Meisei University, The University of Tokyo (UTokyo), Leiden Observatory [Leiden], Universiteit Leiden, Johns Hopkins University (JHU), Instituto de Astrofísica e Ciências do Espaço (IASTRO), University of Maryland [College Park], University of Maryland System, NASA Ames Research Center (ARC), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Météo-France -Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Météo-France, Institut de RadioAstronomie Millimétrique (IRAM), Centre National de la Recherche Scientifique (CNRS), Signal et Communications (IRIT-SC), Institut de recherche en informatique de Toulouse (IRIT), Université Toulouse Capitole (UT Capitole), Université de Toulouse (UT)-Université de Toulouse (UT)-Université Toulouse - Jean Jaurès (UT2J), Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Toulouse Mind & Brain Institut (TMBI), Université Toulouse - Jean Jaurès (UT2J), Université de Toulouse (UT)-Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université Toulouse Capitole (UT Capitole), Université de Toulouse (UT), Institut National Polytechnique (Toulouse) (Toulouse INP), Onsala Space Observatory (OSO), Chalmers University of Technology [Göteborg], Delft University of Technology (TU Delft), Universidade Federal de Itajubá, Bay Area Environmental Research Institute (BAER), Australian Synchrotron [Clayton], INAF - Osservatorio Astrofisico di Catania (OACT), Istituto Nazionale di Astrofisica (INAF), University of Zagreb, Laboratoire de physique de l'ENS - ENS Paris (LPENS), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Département de Physique de l'ENS-PSL, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), University of Colorado [Boulder], Institute for Molecules and Materials [Nijmegen], Radboud University [Nijmegen], Wellesley College, Laboratoire de Physique des 2 Infinis Irène Joliot-Curie (IJCLab), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Institut de Physique de Rennes (IPR), Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS), University of British Columbia (UBC), National Radio Astronomy Observatory [Charlottesville] (NRAO), National Radio Astronomy Observatory (NRAO), European Space Astronomy Centre (ESAC), Agence Spatiale Européenne = European Space Agency (ESA), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University-Smithsonian Institution, Institut d'Astrophysique de Paris (IAP), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Institut Universitaire de France (IUF), Ministère de l'Education nationale, de l’Enseignement supérieur et de la Recherche (M.E.N.E.S.R.), Rice University [Houston], Yunnan Observatories, Chinese Academy of Sciences [Changchun Branch] (CAS), Universidad de Chile = University of Chile [Santiago] (UCHILE), University of Virginia, Aarhus University [Aarhus], Friedrich-Schiller-Universität = Friedrich Schiller University Jena [Jena, Germany], Instituto de Astronomia, Geofísica e Ciências Atmosféricas [São Paulo] (IAG), Universidade de São Paulo = University of São Paulo (USP), San Jose State University [San Jose] (SJSU), European Southern Observatory (ESO), Academia Sinica Institute of Astronomy and Astrophysics (ASIAA), Academia Sinica, Institute of Astronomy of the Russian Academy of Sciences (INASAN), Russian Academy of Sciences [Moscow] (RAS), UK Astronomy Technology Centre (UK ATC), Science and Technology Facilities Council (STFC), Telespazio, Services par satellites, Infrared Processing and Analysis Center (IPAC), California Institute of Technology (CALTECH), University of Missouri [Columbia] (Mizzou), University of Missouri System, Max Planck Institute for Astronomy (MPIA), CAS Key Laboratory of Crust–Mantle Materials and Environments [Hefei], School of Earth and Space Sciences [Hefei], University of Science and Technology of China [Hefei] (USTC)-University of Science and Technology of China [Hefei] (USTC)-Chinese Academy of Sciences [Beijing] (CAS), Lawrence Berkeley National Laboratory [Berkeley] (LBNL), University of California [Berkeley] (UC Berkeley), University of California (UC), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Institut des Sciences Moléculaires (ISM), Université Montesquieu - Bordeaux 4-Université Sciences et Technologies - Bordeaux 1 (UB)-École Nationale Supérieure de Chimie et de Physique de Bordeaux (ENSCPB)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Massachusetts Institute of Technology (MIT), Instituto de Ciencia de Materiales de Madrid (ICMM), Helsingin yliopisto = Helsingfors universitet = University of Helsinki, Steward Observatory, University of Arizona, INAF - Osservatorio Astronomico di Cagliari (OAC), United Arab Emirates University (UAEU), National Astronomical Observatory of Japan (NAOJ), Banaras Hindu University [Varanasi] (BHU), University of Amsterdam [Amsterdam] (UvA), Laboratoire de Chimie et Physique Quantiques Laboratoire (LCPQ), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Fédération de recherche « Matière et interactions » (FeRMI), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), Universidade Federal do Rio Grande do Sul [Porto Alegre] (UFRGS), University of California [San Diego] (UC San Diego), University of Nottingham, UK (UON), Ohio State University [Columbus] (OSU), Space Science Institute [Boulder] (SSI), Stockholm University, Texas State University, Ritter Astrophysical Research Center, University of Toledo, National Sun Yat-Sen University (NSYSU), Star and Planet Formation Laboratory, ITA, USA, GBR, FRA, DEU, ESP, AUS, BEL, BRA, CHL, TWN, HRV, DNK, JPN, IND, NLD, PRT, CHN, RUS, SWE, National Aeronautics and Space Administration (US), University of Maryland, University of Michigan, Centre National de la Recherche Scientifique (France), Centre National D'Etudes Spatiales (France), Natural Sciences and Engineering Research Council of Canada, Ministerio de Ciencia e Innovación (España), German Research Foundation, Japan Society for the Promotion of Science, San José State University Research Foundation, Berné, Olivier, Habart, Émilie, Peeters, Els, Abergel, Alain, Bergin, Edwin A., Bernard-Salas, Jeronimo, Bron, Emeric, Cami, Jan, Dartois, Emmanuel, Fuente, Asunción, Goicoechea, Javier R., Gordon, Karl D., Okada, Yoko, Onaka, Takashi, Robberto, Massimo, Röllig, Markus, Tielens, Alexander G.G.M., Vicente, Sílvia, Wolfire, Mark G., Alarcón, Felipe, Boersma, C., Canin, Amélie, Chown, Ryan, Dicken, Daniel, Le Gal, Romane, Pound, Marc W., Trahin, Boris, Sidhu, Ameek, Van De Putte, Dries, Cuadrado, Sara, Guilloteau, Claire, Maragkoudakis, Alexandros, Schefter, Bethany R., Schirmer, Thiébaut, Aleman, Isabel, Allamandola, Louis, Auchettl, Rebecca, Antonio Baratta, Giuseppe, Bejaoui, Salma, Bera, Partha P., Bilalbegović, Goranka, Black, John H., Boulanger, Francois, Bouwman, Jordy, Brandl, Bernhard, Brünken, Sandra, Burkhardt, Andrew, Candian, Alessandra, Cernicharo, José, Chakraborty, Shubhadip, Champion, Jason, Colgan, Sean W.J., Cooke, Ilsa R., Coutens, Audrey, Cox, Nick L.J., Demyk, Karine, Donovan Meyer, Jennifer, Engrand, Cécile, Foschino, Sacha, Gavilan, Lisseth, Gerin, Maryvonne, Godard, Marie, Gottlieb, Carl A., Guillard, Pierre, Gusdorf, Antoine, Hartigan, Patrick, He, Jinhua, Herbst, Eric, Hornekaer, Liv, Janot-Pacheco, Eduardo, Joblin, Christine, Kaufman, Michael, Kemper, Francisca, Kendrew, Sarah, Kirsanova, Maria S., Klaassen, Pamela, Knight, Collin, Kwok, Sun, Labiano, Álvaro, Lai, Thomas S.Y., Lee, Timothy J., Lefloch, Bertrand, Le Petit, Franck, Li, Aigen, Linz, Hendrik, MacKie, Cameron J., Madden, Suzanne C., Mascetti, Joëlle, McGuire, Brett A., Merino, Pablo, Micelotta, Elisabetta R., Morse, Jon A., Molecular Spectroscopy (HIMS, FNWI), and HIMS (FNWI)

Subjects
Gaseous Nebulae, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, FELIX Infrared and Terahertz Spectroscopy, Star Forming Regions, Astrophysics - Astrophysics of Galaxies, Infrared Telescopes, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Astrophysics::Solar and Stellar Astrophysics, [INFO]Computer Science [cs], Photodissociation Regions, Astrophysics::Earth and Planetary Astrophysics, Polycyclic Aromatic Hydrocarbons, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], James Webb Space Telescope (JWST), Photo-Dissociation Regions (PDRs), Massive stars, Orion Bar, MIRI, NIRSpec, NIRCam, Astrophysics::Galaxy Astrophysics
Abstract

22 pags., 8 figs., 1 tab., Massive stars disrupt their natal molecular cloud material through radiative and mechanical feedback processes. These processes have profound effects on the evolution of interstellar matter in our Galaxy and throughout the universe, from the era of vigorous star formation at redshifts of 1-3 to the present day. The dominant feedback processes can be probed by observations of the Photo-Dissociation Regions (PDRs) where the far-ultraviolet photons of massive stars create warm regions of gas and dust in the neutral atomic and molecular gas. PDR emission provides a unique tool to study in detail the physical and chemical processes that are relevant for most of the mass in inter-and circumstellar media including diffuse clouds, proto-planetary disks, and molecular cloud surfaces, globules, planetary nebulae, and star-forming regions. PDR emission dominates the infrared (IR) spectra of star-forming galaxies. Most of the Galactic and extragalactic observations obtained with the James Webb Space Telescope (JWST) will therefore arise in PDR emission. In this paper we present an Early Release Science program using the MIRI, NIRSpec, and NIRCam instruments dedicated to the observations of an emblematic and nearby PDR: the Orion Bar. These early JWST observations will provide template data sets designed to identify key PDR characteristics in JWST observations. These data will serve to benchmark PDR models and extend them into the JWST era. We also present the Science-Enabling products that we will provide to the community. These template data sets and Science-Enabling products will guide the preparation of future proposals on star-forming regions in our Galaxy and beyond and will facilitate data analysis and interpretation of forthcoming JWST observations., Support for JWST-ERS program ID 1288 was provided through grants from the STScI under NASA contract NAS5-03127 to STScI (K.G., D.V.D.P., M.R.), Univ. of Maryland (M.W., M.P.), Univ. of Michigan (E.B., F.A.), and Univ. of Toledo (T.S.-Y.L.). O.B. and E.H. are supported by the Programme National “Physique et Chimie du Milieu Interstellaire” (PCMI) of CNRS/INSU with INC/INP co-funded by CEA and CNES, and through APR grants 6315 and 6410 provided by CNES. E. P. and J.C. acknowledge support from the National Science and Engineering Council of Canada (NSERC) Discovery Grant program (RGPIN-2020-06434 and RGPIN-2021-04197 respectively). E.P. acknowledges support from a Western Strategic Support Accelerator Grant (ROLA ID 0000050636). J.R.G. and S.C. thank the Spanish MCINN for funding support under grant PID2019-106110GB-I00. Work by M.R. and Y.O. is carried out within the Collaborative Research Centre 956, subproject C1, funded by the Deutsche Forschungsgemeinschaft (DFG)—project ID 184018867. T.O. acknowledges support from JSPS Bilateral Program, grant No. 120219939. M.P. and M.W. acknowledge support from NASA Astrophysics Data Analysis Program award #80NSSC19K0573. C.B. is grateful for an appointment at NASA Ames Research Center through the San José State University Research Foundation (NNX17AJ88A) and acknowledges support from the Internal Scientist Funding Model (ISFM) Directed Work Package at NASA Ames titled: “Laboratory Astrophysics—The NASA Ames PAH IR Spectroscopic Database.”

Published
2022
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4. SOFIA FIFI-LS Observations of Sgr B1: Ionization Structure and Sources of Excitation

Author

Angela S. Cotera, Susan R. Stolovy, Michael Kaufman, Sean W. J. Colgan, and Janet P. Simpson

Subjects
Physics, Supermassive black hole, 010308 nuclear & particles physics, Star formation, Molecular cloud, Astrophysics::High Energy Astrophysical Phenomena, Galactic Center, Doubly ionized oxygen, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Astrophysics - Astrophysics of Galaxies, Common envelope, Stars, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, O-type star
Abstract

The current paradigm of Galactic Center (GC) gas motions and star formation envisions sequential star formation in streams of gas as they pass near the supermassive black hole, Sgr A*. This is based on the relative positions of dense molecular clouds, the very young star-forming region Sgr B2, the much older region Sgr C, and the several Myr old Arches and Quintuplet Clusters. Because Sgr B1 is found with Sgr B2 in a common envelope of molecular gas and far-infrared emission, the two sources are thought to be physically related, even though there are indicators of a significantly greater age for Sgr B1. To clarify the status of Sgr B1, we have mapped it with the FIFI-LS spectrometer on SOFIA in the far-infrared lines of [O III] 52 and 88 micron. From the ratios of these lines and lines measured with the Spitzer Infrared Spectrograph, we find that there are at least eight separate sub-regions that must contain the stars that excite the gas. We infer spectral energy distributions (SEDs) of the ionizing sources from models and find they are in agreement only with SEDs of late O stars augmented at the highest frequencies with interstellar X-rays from fast shocks. We suggest that although the gas, from its velocity structure, must be part of the very young Sgr B2 complex, the stars that are ionizing the gas were not formed there but are the remnants of a previous generation of star formation in the GC., 9 pages, 3 figures. Accepted by ApJL. New version fixes typos and updates references

Published
2018

5. High Spectral Resolution SOFIA/EXES Observations of C2H2 towards Orion-IRc2

Author

Matthew J. Richter, Timothy J. Lee, Xinchuan Huang, Mark E. McKelvey, Naseem Rangwala, Romane Le Gal, Adwin Boogert, Eric Herbst, Sean W. J. Colgan, Kinsuk Acharyya, and C. DeWitt

Subjects
Physics, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), 0103 physical sciences, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Spectral resolution, 010306 general physics, 010303 astronomy & astrophysics, 01 natural sciences, Astrophysics - Astrophysics of Galaxies
Abstract

We present high-spectral resolution observations from 12.96 - 13.33 microns towards Orion IRc2 using the mid-infrared spectrograph, EXES, on SOFIA. These observations probe the physical and chemical conditions of the Orion hot core, which is sampled by a bright, compact, mid-infrared background continuum source in the region, IRc2. All ten of the rovibrational C2H2 transitions expected in our spectral coverage, are detected with high S/N, yielding continuous coverage of the R-branch lines from J=9-8 to J=18-17, including both ortho and para species. Eight of these rovibrational transitions are newly reported detections. The isotopologue, 13CCH2, is clearly detected with high signal-to-noise. This enabled a direct measurement of the 12C/13C isotopic ratio for the Orion hot core of 14 +/- 1 and an estimated maximum value of 21. We also detected several HCN rovibrational lines. The ortho and para C2H2 ladders are clearly separate and tracing two different temperatures, 226 K and 164 K, respectively, with a non-equilibrium ortho to para ratio (OPR) of 1.7 +\- 0.1. Additionally, the ortho and para V_LSR values differ by about 1.8 +/- 0.2 km/s, while, the mean line widths differ by 0.7 +/- 0.2 km/s, suggesting that these species are not uniformly mixed along the line of sight to IRc2. We propose that the abnormally low C2H2 OPR could be a remnant from an earlier, colder phase, before the density enhancement (now the hot core) was impacted by shocks generated from an explosive event 500 yrs ago., accepted for publication in The Astrophysical Journal

Published
2017

6. Spitzer observations of extragalactic H II regions - III. NGC 6822 and the hot star, H II region connection

Author

I. A. McNabb, Justin Kader, Johann A. Weber, Adalbert W. A. Pauldrach, Sean W. J. Colgan, Janet P. Simpson, Reginald J. Dufour, and Robert H. Rubin

Subjects
H II region, Metallicity, chemistry.chemical_element, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Neon, Spitzer Space Telescope, Ionization, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Emission spectrum, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Physics, 010308 nuclear & particles physics, Stellar atmosphere, Astronomy, Astronomy and Astrophysics, Astrophysics - Astrophysics of Galaxies, chemistry, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Astrophysics::Earth and Planetary Astrophysics, Irregular galaxy
Abstract

Using the short-high module of the Infrared Spectrograph on the Spitzer Space Telescope, we have measured the [S IV] 10.51, [Ne II] 12.81, [Ne III] 15.56, and [S III] 18.71-micron emission lines in nine H II regions in the dwarf irregular galaxy NGC 6822. These lines arise from the dominant ionization states of the elements neon (Ne$^{++}$, Ne$^+$) and sulphur (S$^{3+}$, S$^{++}$), thereby allowing an analysis of the neon to sulphur abundance ratio as well as the ionic abundance ratios Ne$^+$/Ne$^{++}$ and S$^{3+}$/S$^{++}$. By extending our studies of H II regions in M83 and M33 to the lower metallicity NGC 6822, we increase the reliability of the estimated Ne/S ratio. We find that the Ne/S ratio appears to be fairly universal, with not much variation about the ratio found for NGC 6822: the median (average) Ne/S ratio equals 11.6 (12.2$\pm$0.8). This value is in contrast to Asplund et al.'s currently best estimated value for the Sun: Ne/S = 6.5. In addition, we continue to test the predicted ionizing spectral energy distributions (SEDs) from various stellar atmosphere models by comparing model nebulae computed with these SEDs as inputs to our observational data, changing just the stellar atmosphere model abundances. Here we employ a new grid of SEDs computed with different metallicities: Solar, 0.4 Solar, and 0.1 Solar. As expected, these changes to the SED show similar trends to those seen upon changing just the nebular gas metallicities in our plasma simulations: lower metallicity results in higher ionization. This trend agrees with the observations., 22 pages, 13 figures. To be published in MNRAS. reference added and typos fixed. arXiv admin note: text overlap with arXiv:0804.0828, which is paper II by Rubin et al. (2008)

Published
2016

8. High Spectral Resolution SOFIA/EXES Observations of C2H2 toward Orion IRc2.

Author

Naseem Rangwala, Sean W. J. Colgan, Romane Le Gal, Kinsuk Acharyya, Xinchuan Huang, Timothy J. Lee, Eric Herbst, Curtis deWitt, Matt Richter, Adwin Boogert, and Mark McKelvey

Subjects
*ASTRONOMICAL observations, *SIGNAL-to-noise ratio, *ISOTOPOLOGUES, *ORION (Spacecraft), *SPECTRUM analysis
Abstract

We present high spectral resolution observations from 12.96 to 13.33 microns toward Orion IRc2 using the mid-infrared spectrograph, Echelon-Cross-Echelle Spectrograph (EXES), at Stratospheric Observatory for Infrared Astronomy (SOFIA). These observations probe the physical and chemical conditions of the Orion hot core, which is sampled by a bright, compact, mid-infrared background continuum source in the region, IRc2. All 10 of the rovibrational C2H2 transitions expected in our spectral coverage are detected with high signal-to-noise ratios (S/Ns), yielding continuous coverage of the R-branch lines from J = 9–8 to J = 18–17, including both ortho and para species. Eight of these rovibrational transitions are newly reported detections. The isotopologue, 13CCH2, is clearly detected with a high S/N. This enabled a direct measurement of the 12C/13C isotopic ratio for the Orion hot core of 14 ± 1 and an estimated maximum value of 21. We also detected several HCN rovibrational lines. The ortho and para C2H2 ladders are clearly separate, and tracing two different temperatures, 226 K and 164 K, respectively, with a non-equilibrium ortho to para ratio (OPR) of 1.7 ± 0.1. Additionally, the ortho and para VLSR values differ by about 1.8 ± 0.2 km s−1, while the mean line widths differ by 0.7 ± 0.2 km s−1, suggesting that these species are not uniformly mixed along the line of sight to IRc2. We propose that the abnormally low C2H2 OPR could be a remnant from an earlier, colder phase, before the density enhancement (now the hot core) was impacted by shocks generated from an explosive event 500 years ago. [ABSTRACT FROM AUTHOR]

Published
2018
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