A STUDY OF HEATING AND COOLING OF THE ISM IN NGC 1097 WITH HERSCHEL-PACS AND SPITZER-IRS
- Spitzer Science Center, California Institute of Technology, Pasadena, CA 91125 (United States)
- Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125 (United States)
- NASA Herschel Science Center, California Institute of Technology, Pasadena, CA 91125 (United States)
- Department of Physics and Astronomy, Mail Drop 111, University of Toledo, 2801 West Bancroft Street, Toledo, OH 43606 (United States)
- Carnegie Observatories, Pasadena, CA 91101 (United States)
- Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071 (United States)
- Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States)
- Department of Astronomy, University of Maryland, College Park, MD 20742 (United States)
- Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, 69117 Heidelberg (Germany)
- Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden (Netherlands)
- Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States)
- Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States)
NGC 1097 is a nearby Seyfert 1 galaxy with a bright circumnuclear starburst ring, a strong large-scale bar, and an active nucleus. We present a detailed study of the spatial variation of the far-infrared (FIR) [C II]158 {mu}m and [O I]63 {mu}m lines and mid-infrared H{sub 2} emission lines as tracers of gas cooling, and of the polycyclic aromatic hydrocarbon (PAH) bands as tracers of the photoelectric heating, using Herschel-PACS and Spitzer-IRS infrared spectral maps. We focus on the nucleus and the ring, and two star-forming regions (Enuc N and Enuc S). We estimated a photoelectric gas heating efficiency ([C II]158 {mu}m+[O I]63 {mu}m)/PAH in the ring about 50% lower than in Enuc N and S. The average 11.3/7.7 {mu}m PAH ratio is also lower in the ring, which may suggest a larger fraction of ionized PAHs, but no clear correlation with [C II]158 {mu}m/PAH(5.5-14 {mu}m) is found. PAHs in the ring are responsible for a factor of two more [C II]158 {mu}m and [O I]63 {mu}m emission per unit mass than PAHs in the Enuc S. spectral energy distribution (SED) modeling indicates that at most 25% of the FIR power in the ring and Enuc S can come from high-intensity photodissociation regions (PDRs), in which case G{sub 0} {approx} 10{sup 2.3} and n{sub H} {approx} 10{sup 3.5} cm{sup -3} in the ring. For these values of G{sub 0} and n{sub H}, PDR models cannot reproduce the observed H{sub 2} emission. Much of the H{sub 2} emission in the starburst ring could come from warm regions in the diffuse interstellar medium that are heated by turbulent dissipation or shocks.
- OSTI ID:
- 22037150
- Journal Information:
- Astrophysical Journal, Vol. 751, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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