A Molecular Gas Ring Hidden in the Sombrero Galaxy
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Jessica Sutter
UC San Diego
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The interplay between heating and cooling within the interstellar medium (ISM) is crucial for the regulation of ongoing star formation and therefore plays a key role in galaxy evolution. While the heating of the ISM can be traced by dust emission (either through PAH emission or far-infrared luminosity), cooling occurs via fine structure line emission, like the 158μm singly-ionized carbon line, [CII]. By comparing heating and cooling tracers in a wide variety of galaxy types, inclinations, and ISM conditions, we can assess what conditions limit the photoelectric heating efficiency and therefore could hamper potential future star formation. In addition, as the balance between heating and cooling is essential for using the [CII] line as proxy of star formation rate (SFR), determining where this balance is upset provides crucial constraints on its applicability to trace SFR in distant galaxies. Building off analysis of the spatially resolved [CII] emission in spiral galaxy NGC7331, we examine the [CII] emission in the Sombrero galaxy and its relationship with CO, Hα, and total infrared emission. Through comparisons with archival FIFI-LS and PACS [CII] data of nearby galaxies, we find that the Sombrero galaxy seems to follow trends similar to those of nearby early-type galaxies, which all show [CII]/FIR values lower than those observed in similar regions in NGC7331. This likely indicates that different heating mechanisms, e.g. the prevalence of an older stellar population, can alter the proportionality between [CII] and FIR emission.