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A study of heating and cooling of the ISM in NGC 1097 with Herschel-pacs and Spitzer-IRS

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Gil de Paz, Armando and otros, ... (2012) A study of heating and cooling of the ISM in NGC 1097 with Herschel-pacs and Spitzer-IRS. Astrophysical journal, 751 (2). ISSN 0004-637X

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Official URL: http://dx.doi.org/10.1088/0004-637X/751/2/144


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http://iopscience.iop.org/Publisher


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) [C II]158 μm and [O I]63 μm lines and mid-infrared H2 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 μm+[O I]63 μm)/PAH in the ring about 50% lower than in Enuc N and S. The average 11.3/7.7 μm 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 μm/PAH(5.5-14 μm) is found. PAHs in the ring are responsible for a factor of two more [C II]158 μm and [O I]63 μm 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 ~ 10^2.3 and n_H ~ 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.


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© 2012. The American Astronomical Society. All rights reserved. Artículo firmado por 41 autores. We thank Gregory Brunner and Sebastian Haan for the code used to construct the Spitzer-IRS maps. We also thank Dario Fadda and Jeff Jacobson for software support. This work is partially based on observations made with Herschel, a European Space Agency Cornerstone Mission with significant participation by NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech. 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); and 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). Data presented in this paper were analyzed using The Herschel Interactive Processing Environment (HIPE), a joint development by the Herschel Science Ground Segment Consortium, consisting of ESA, the NASA Herschel Science Center, and the HIFI, PACS, and SPIRE consortia.

Uncontrolled Keywords:Far-infrared spectroscopy; Nearby galaxies survey; Star-forming galaxies; Interstellar-medium; C-ii; Photodissociation regions; Molecular-hydrogen; Translucent clouds; Seyfert-galaxies; Iron project
Subjects:Sciences > Physics > Astrophysics
Sciences > Physics > Astronomy
ID Code:35183
Deposited On:22 Jan 2016 16:36
Last Modified:10 Dec 2018 15:05

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