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arXiv · 1404.0403

The physical characteristics of the gas in the disk of Centaurus A using the Herschel Space Observatory

T. J. Parkin·C. D. Wilson·M. R. P. Schirm·M. Baes·M. Boquien·A. Boselli·D. Cormier·M. Galametz·O. Ł. Karczewski·V. Lebouteiller·I. De Looze·S. C. Madden·H. Roussel·M. W. L. Smith·L. Spinoglio
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Abstract

We search for variations in the disk of Centaurus A of the emission from atomic fine structure lines using Herschel PACS and SPIRE spectroscopy. In particular we observe the [C II](158 $μ$m), [N II](122 and 205 $μ$m), [O I](63 and 145 $μ$m) and [O III](88 $μ$m) lines, which all play an important role in cooling the gas in photo-ionized and photodissociation regions. We determine that the ([C II]+[O I]$_{63}$)/$F_{TIR}$ line ratio, a proxy for the heating efficiency of the gas, shows no significant radial trend across the observed region, in contrast to observations of other nearby galaxies. We determine that 10 - 20% of the observed [C II] emission originates in ionized gas. Comparison between our observations and a PDR model shows that the strength of the far-ultraviolet radiation field, $G_0$, varies between $10^{1.75}$ and $10^{2.75}$ and the hydrogen nucleus density varies between $10^{2.75}$ and $10^{3.75}$ cm$^{-3}$, with no significant radial trend in either property. In the context of the emission line properties of the grand-design spiral galaxy M51 and the elliptical galaxy NGC 4125, the gas in Cen A appears more characteristic of that in typical disk galaxies rather than elliptical galaxies.

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T. J. Parkin, C. D. Wilson, M. R. P. Schirm, M. Baes, M. Boquien, A. Boselli, D. Cormier, M. Galametz, O. Ł. Karczewski, V. Lebouteiller, I. De Looze, S. C. Madden, H. Roussel, M. W. L. Smith, L. Spinoglio. 2014-04-01. The physical characteristics of the gas in the disk of Centaurus A using the Herschel Space Observatory. https://doi.org/10.1088/0004-637x%2F787%2F1%2F16

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