HERSCHEL-SPIRE IMAGING SPECTROSCOPY OF MOLECULAR GAS IN M82

Journal Article · Sun Jul 01 00:00:00 EDT 2012 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/753/1/70· OSTI ID:22036889

Kamenetzky, J; Glenn, J; Rangwala, N; Maloney, P ^[1]; Bradford, M ^[2]; Wilson, C D; Schirm, M R. P. ^[3]; Bendo, G J ^[4]; Baes, M ^[5]; Boselli, A ^[6]; Cooray, A ^[7]; Isaak, K G ^[8]; Lebouteiller, V; Madden, S; Panuzzo, P; Wu, R ^[9]; Spinoglio, L ^[10]

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1. Center for Astrophysics and Space Astronomy, 389-UCB, University of Colorado, Boulder, CO 80303 (United States)
2. NASA Jet Propulsion Laboratory, Pasadena, CA 91109 (United States)
3. Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S 4M1 (Canada)
4. UK ALMA Regional Centre Node, Jordell Bank Center for Astrophysics, School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL (United Kingdom)
5. Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281 S9, 9000 Gent (Belgium)
6. Laboratoire d'Astrophysique de Marseille, UMR6110 CNRS, 38 rue F. Joliot-Curie, 13388 Marseille (France)
7. Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States)
8. ESA Astrophysics Missions Division, ESTEC, P.O. Box 299, 2200 AG Noordwijk (Netherlands)
9. CEA, Laboratoire AIM, Irfu/SAp, Orme des Merisiers, 91191 Gif-sur-Yvette (France)
10. Istituto di Fisica dello Spazio Interplanetario, INAF, Via del Fosso del Cavaliere 100, 00133 Roma (Italy)

We present new Herschel-SPIRE imaging spectroscopy (194-671 {mu}m) of the bright starburst galaxy M82. Covering the CO ladder from J = 4 {yields} 3 to J = 13 {yields} 12, spectra were obtained at multiple positions for a fully sampled {approx}3 Multiplication-Sign 3 arcmin map, including a longer exposure at the central position. We present measurements of {sup 12}CO, {sup 13}CO, [C I], [N II], HCN, and HCO{sup +} in emission, along with OH{sup +}, H{sub 2}O{sup +}, and HF in absorption and H{sub 2}O in both emission and absorption, with discussion. We use a radiative transfer code and Bayesian likelihood analysis to model the temperature, density, column density, and filling factor of multiple components of molecular gas traced by {sup 12}CO and {sup 13}CO, adding further evidence to the high-J lines tracing a much warmer ({approx}500 K), less massive component than the low-J lines. The addition of {sup 13}CO (and [C I]) is new and indicates that [C I] may be tracing different gas than {sup 12}CO. No temperature/density gradients can be inferred from the map, indicating that the single-pointing spectrum is descriptive of the bulk properties of the galaxy. At such a high temperature, cooling is dominated by molecular hydrogen. Photon-dominated region (PDR) models require higher densities than those indicated by our Bayesian likelihood analysis in order to explain the high-J CO line ratios, though cosmic-ray-enhanced PDR models can do a better job reproducing the emission at lower densities. Shocks and turbulent heating are likely required to explain the bright high-J emission.

• OSTI ID: 22036889
• Journal Information: Astrophysical Journal, Vol. 753, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ABSORPTION
ABSORPTION SPECTROSCOPY
ASTRONOMY
ASTROPHYSICS
CARBON MONOXIDE
COSMIC PHOTONS
DENSITY
EMISSION
EMISSION SPECTRA
EMISSION SPECTROSCOPY
GALAXIES
HYDROCYANIC ACID
HYDROFLUORIC ACID
HYDROGEN
HYDROXIDES
MOLECULES
RADIANT HEAT TRANSFER
TURBULENT HEATING
WATER