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Author(s): Beirao, P; Armus, L; Helou, G; Appleton, PN; Smith, J-DT; et al

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Abstract: 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) [CII]158 mu m and [OI]63 mu m lines and mid-infrared H-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 ([CII]158 mu m+[OI]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 [CII]158 mu m/PAH(5.5-14 mu m) is found. PAHs in the ring are responsible for a factor of two more [CII]158 mu m and [OI]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(0) similar to 10(2.3) and n(H) similar to 10(3.5) cm(-3) in the ring. For these values of G(0) and n(H), PDR models cannot reproduce the observed H-2 emission. Much of the H-2 emission in the starburst ring could come from warm regions in the diffuse interstellar medium that are heated by turbulent dissipation or shocks.
Publication Date: 1-Jun-2012
Electronic Publication Date: 16-May-2012
Citation: Beirao, P, Armus, L, Helou, G, Appleton, PN, Smith, J-DT, Croxall, KV, Murphy, EJ, Dale, DA, Draine, BT, Wolfire, MG, Sandstrom, KM, Aniano, G, Bolatto, AD, Groves, B, Brandl, BR, Schinnerer, E, Crocker, AF, Hinz, JL, Rix, H-W, Kennicutt, RC, Calzetti, D, Gil de Paz, A, Dumas, G, Galametz, M, Gordon, KD, Hao, C-N, Johnson, B, Koda, J, Krause, O, van der Laan, T, Leroy, AK, Li, Y, Meidt, SE, Meyer, JD, Rahman, N, Roussel, H, Sauvage, M, Srinivasan, S, Vigroux, L, Walter, F, Warren, BE. (2012). A STUDY OF HEATING AND COOLING OF THE ISM IN NGC 1097 WITH HERSCHEL-PACS AND SPITZER-IRS. ASTROPHYSICAL JOURNAL, 751 (10.1088/0004-637X/751/2/144
DOI: doi:10.1088/0004-637X/751/2/144
ISSN: 0004-637X
Type of Material: Journal Article
Journal/Proceeding Title: ASTROPHYSICAL JOURNAL
Version: Final published version. Article is made available in OAR by the publisher's permission or policy.
Notes: Supplementary data may be available at , and

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