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

Abstract

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{sub 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.

Authors:
;  [1]; ;  [2]; ;  [3];  [4];  [5]
  1. Department of Astronomy, University of Michigan, 1085 S. University Avenue, Ann Arbor, MI 48109 (United States)
  2. Grupo de Astrofísica Molecular, Instituto de Ciencia de Materiales de Madrid (CSIC) E-28049 Madrid (Spain)
  3. LERMA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC Univ. Paris 06, École normale supérieure, F-75005, Paris (France)
  4. LERMA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC Univ. Paris 06, F-75014, Paris (France)
  5. I. Physikalisches Institut der Universität zu Köln, Zülpicher Str. 77, D-50937 Köln (Germany)
Publication Date:
OSTI Identifier:
22663809
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 836; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BEAMS; CARBON; CARBON MONOXIDE; EMISSION; ENERGY SPECTRA; EXCITATION; GALAXIES; HEAT EXCHANGERS; MOLECULES; MONOCLINIC LATTICES; PERTURBED ANGULAR CORRELATION; STARS

Citation Formats

Indriolo, Nick, Bergin, E. A., Goicoechea, J. R., Cernicharo, J., Gerin, M., Gusdorf, A., Lis, D. C., and Schilke, P., E-mail: nindriolo@stsci.edu. CO Spectral Line Energy Distributions in Galactic Sources: Empirical Interpretation of Extragalactic Observations. United States: N. p., 2017. Web. doi:10.3847/1538-4357/836/1/117.
Indriolo, Nick, Bergin, E. A., Goicoechea, J. R., Cernicharo, J., Gerin, M., Gusdorf, A., Lis, D. C., & Schilke, P., E-mail: nindriolo@stsci.edu. CO Spectral Line Energy Distributions in Galactic Sources: Empirical Interpretation of Extragalactic Observations. United States. doi:10.3847/1538-4357/836/1/117.
Indriolo, Nick, Bergin, E. A., Goicoechea, J. R., Cernicharo, J., Gerin, M., Gusdorf, A., Lis, D. C., and Schilke, P., E-mail: nindriolo@stsci.edu. Fri . "CO Spectral Line Energy Distributions in Galactic Sources: Empirical Interpretation of Extragalactic Observations". United States. doi:10.3847/1538-4357/836/1/117.
@article{osti_22663809,
title = {CO Spectral Line Energy Distributions in Galactic Sources: Empirical Interpretation of Extragalactic Observations},
author = {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., E-mail: nindriolo@stsci.edu},
abstractNote = {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{sub 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.},
doi = {10.3847/1538-4357/836/1/117},
journal = {Astrophysical Journal},
number = 1,
volume = 836,
place = {United States},
year = {Fri Feb 10 00:00:00 EST 2017},
month = {Fri Feb 10 00:00:00 EST 2017}
}
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