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

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 $\mu$m), [N II](122 and 205 $\mu$m), [O I](63 and 145 $\mu$m) and [O III](88 $\mu$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.

Accepted for publication in the Astrophysical Journal. 22 pages, 10 figures, 5 tables

References in corpus (9)

• Spectral Mapping Reconstruction of Extended Sources
• A Compendium of Far-Infrared Line and Continuum Emission for 227 Galaxies Observed by the Infrared Space Observatory
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• Detection of the 205 um [NII] Line from the Carina Nebula
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• Insights into gas heating and cooling in the disc of NGC 891 from Herschel far-infrared spectroscopy
• The outflow of gas from the Centaurus A circumnuclear disk: atomic spectral line maps from Herschel-PACS and APEX
• Gas and dust cooling along the major axis of M33 (HerM33es) -- Herschel/PACS [CII] and [OI] observations
• Heating and cooling of the neutral ISM in the NGC4736 circumnuclear ring
• A Giant Molecular Cloud Catalog in the Molecular Disk of the Elliptical Galaxy NGC 5128 (Centaurus A)
• The interstellar medium in Andromeda's dwarf spheroidal galaxies: II. Multi-phase gas content and ISM conditions