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CO Spectral Line Energy Distributions in Galactic Sources: Empirical Interpretation of Extragalactic Observations

Indriolo, Nick and Bergin, E. A. and Goicoechea, J. R. and Cernicharo, J. and Gerin, M. and Gusdorf, A. and Lis, D. C. and Schilke, P. (2017) CO Spectral Line Energy Distributions in Galactic Sources: Empirical Interpretation of Extragalactic Observations. Astrophysical Journal, 836 (1). Art. No. 117. ISSN 0004-637X. doi:10.3847/1538-4357/836/1/117.

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The relative populations in rotational transitions of CO can be useful for inferring gas conditions and excitation mechanisms at work in the interstellar medium. We present CO emission lines from rotational transitions observed with Herschel/HIFI in the star-forming cores Orion S, Orion KL, Sgr B2(M), and W49N. Integrated line fluxes from these observations are combined with those from Herschel/PACS observations of the same sources to construct CO spectral line energy distributions (SLEDs) from 5 ≤ J_u ≤ 48. These CO SLEDs are compared to those reported in other galaxies, with the intention of empirically determining which mechanisms dominate excitation in such systems. We find that CO SLEDs in Galactic star-forming cores cannot be used to reproduce those observed in other galaxies, although the discrepancies arise primarily as a result of beam filling factors. The much larger regions sampled by the Herschel beams at distances of several megaparsecs contain significant amounts of cooler gas, which dominate the extragalactic CO SLEDs, in contrast to observations of Galactic star-forming regions, which are focused specifically on cores containing primarily hot molecular gas.

Item Type:Article
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URLURL TypeDescription Paper
Indriolo, Nick0000-0001-8533-6440
Bergin, E. A.0000-0003-4179-6394
Lis, D. C.0000-0002-0500-4700
Schilke, P.0000-0003-2141-5689
Additional Information:© 2017. The American Astronomical Society. Received 2016 November 15; revised 2016 December 30; accepted 2017 January 12; published 2017 February 13. The authors thank the anonymous referee for suggestions to improve the clarity of the paper. Support for this work was provided by NASA through an award issued by JPL/Caltech. J.R.G. and J.C. thank the ERC for support under grant ERC-2013-Syg-610256-NANOCOSMOS, and the Spanish MINECO for support under grant AYA2012-32032. HIFI has been designed and built by a consortium of institutes and university departments from across Europe, Canada, and the United States under the leadership of SRON Netherlands Institute for Space Research, Groningen, The Netherlands and with major contributions from Germany, France and the US. Consortium members are Canada: CSA, U. Waterloo; France: CESR, LAB, LERMA, IRAM; Germany: KOSMA, MPIfR, MPS; Ireland, NUI Maynooth; Italy: ASI, IFSI-INAF, Osservatorio Astrofisico di Arcetri-INAF; Netherlands: SRON, TUD; Poland: CAMK, CBK; Spain: Observatorio Astronmico Nacional (IGN), Centro de Astrobiologa (CSIC-INTA). Sweden: Chalmers University of Technology—MC2, RSS & GARD; Onsala Space Observatory; Swedish National Space Board, Stockholm University—Stockholm Observatory; Switzerland: ETH Zurich, FHNW; USA: Caltech, JPL, NHSC. PACS has been developed by a consortium of institutes led by MPE (Germany) and including UVIE (Austria); KU Leuven, CSL, IMEC (Belgium); CEA, LAM (France); MPIA (Germany); INAF-IFSI/OAA/OAP/OAT, LENS, SISSA (Italy); IAC (Spain). This development has been supported by the funding agencies BMVIT (Austria), ESA-PRODEX (Belgium), CEA/CNES (France), DLR (Germany), ASI/INAF (Italy), and CICYT/MCYT (Spain).
Funding AgencyGrant Number
European Research Council (ERC)ERC-2013-Syg-610256-NANOCOSMOS
Ministerio de Economía, Industria y Competitividad (MINECO)AYA2012-32032
Subject Keywords:galaxies: ISM; ISM: molecules
Issue or Number:1
Record Number:CaltechAUTHORS:20170213-160413280
Persistent URL:
Official Citation:Nick Indriolo et al 2017 ApJ 836 117
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:74276
Deposited By: George Porter
Deposited On:14 Feb 2017 15:26
Last Modified:11 Nov 2021 05:26

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