Neill, Justin L., Bergin, Edwin A., Lis, Dariusz C., Schilke, Peter, Crockett, Nathan R., Favre, Cecile, Emprechtinger, Martin, Comito, Claudia, Qin, Sheng-Li, Anderson, Dana E., Burkhardt, Andrew M., Chen, Jo-Hsin, Harris, Brent J., Lord, Steven D., McGuire, Brett A., McNeill, Trevor D., Monje, Raquel R., Phillips, Thomas G., Steber, Amanda L., Vasyunina, Tatiana and Yu, Shanshan ORCID: 0000-0002-2472-7998 (2014). HERSCHEL OBSERVATIONS OF EXTRAORDINARY SOURCES: ANALYSIS OF THE FULL HERSCHEL/HIFI MOLECULAR LINE SURVEY OF SAGITTARIUS B2(N). Astrophys. J., 789 (1). BRISTOL: IOP PUBLISHING LTD. ISSN 1538-4357

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Abstract

A sensitive broadband molecular line survey of the Sagittarius B2(N) star-forming region has been obtained with the Heterodyne Instrument for the Far-Infrared (HIFI) instrument on the Herschel Space Observatory, offering the first high spectral resolution look at this well-studied source in a wavelength region largely inaccessible from the ground (625-157 mu m). From the roughly 8000 spectral features in the survey, a total of 72 isotopologues arising from 44 different molecules have been identified, ranging from light hydrides to complex organics, and arising from a variety of environments from cold and diffuse to hot and dense gas. We present a local thermodynamic equilibrium (LTE) model to the spectral signatures of each molecule, constraining the source sizes for hot core species with complementary Submillimeter Array interferometric observations and assuming that molecules with related functional group composition are cospatial. For each molecule, a single model is given to fit all of the emission and absorption features of that species across the entire 480-1910 GHz spectral range, accounting for multiple temperature and velocity components when needed to describe the spectrum. As with other HIFI surveys toward massive star-forming regions, methanol is found to contribute more integrated line intensity to the spectrum than any other species. We discuss the molecular abundances derived for the hot core where the LTE approximation is generally found to describe the spectrum well, in comparison to abundances derived for the same molecules in the Orion KL region from a similar HIFI survey. Notably, we find significantly higher abundances of amine- and amide-bearing molecules (CH3NH2, CH2NH, and NH2CHO) toward Sgr B2(N) than Orion KL and lower abundances of some complex oxygen-bearing molecules (CH3OCHO in particular). In addition to information on the chemical composition of the hot core, the strong far-infrared dust continuum allows a number of molecules to be detected in absorption in the Sgr B2(N) envelope for the first time at high spectral resolution, and we discuss the possible physical origin of the kinematic components observed in absorption. Additionally, from the detection of new HOCO+ transitions in absorption compared to published HCO+ isotopic observations, we discuss constraints on the gas-phase CO2 abundance and compare this to observations of the ice composition in the Galactic center region, and to CO2 abundance estimates toward other high-mass star-forming regions. The reduced HIFI spectral scan and LTE model are made available to the public as a resource for future investigations of star-forming regions in the submillimeter and far-infrared.

Item Type: Journal Article
Creators:
CreatorsEmailORCIDORCID Put Code
Neill, Justin L.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Bergin, Edwin A.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Lis, Dariusz C.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Schilke, PeterUNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Crockett, Nathan R.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Favre, CecileUNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Emprechtinger, MartinUNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Comito, ClaudiaUNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Qin, Sheng-LiUNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Anderson, Dana E.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Burkhardt, Andrew M.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Chen, Jo-HsinUNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Harris, Brent J.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Lord, Steven D.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
McGuire, Brett A.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
McNeill, Trevor D.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Monje, Raquel R.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Phillips, Thomas G.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Steber, Amanda L.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Vasyunina, TatianaUNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Yu, ShanshanUNSPECIFIEDorcid.org/0000-0002-2472-7998UNSPECIFIED
URN: urn:nbn:de:hbz:38-434771
DOI: 10.1088/0004-637X/789/1/8
Journal or Publication Title: Astrophys. J.
Volume: 789
Number: 1
Date: 2014
Publisher: IOP PUBLISHING LTD
Place of Publication: BRISTOL
ISSN: 1538-4357
Language: English
Faculty: Unspecified
Divisions: Unspecified
Subjects: no entry
Uncontrolled Keywords:
KeywordsLanguage
STAR-FORMING REGIONS; INTER-STELLAR CLOUDS; GAS-PHASE CHEMISTRY; SPIRAL ARM CLOUDS; GALACTIC-CENTER; CONTINUUM OBSERVATIONS; SPECTRAL-LINE; ORION-KL; SGR B2; INTERSTELLAR CLOUDSMultiple languages
Astronomy & AstrophysicsMultiple languages
URI: http://kups.ub.uni-koeln.de/id/eprint/43477

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