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arXiv · 2310.02358

Shock enhanced [CII] emission from the infalling galaxy Arp 25

Dario Fadda·Jessica S. Sutter·Robert Minchin·Fiorella Polles
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Abstract

We present SOFIA observations with HAWC+ and FIFI-LS of the peculiar galaxy Arp 25, also known as NGC 2276 or UGC 3740, whose morphology is deformed by its impact with the intra-group medium of the NGC 2300 galaxy group. These observations show the first direct proof of the enhancement of [CII] emission due to shocks caused by ram pressure in a group of galaxies. By comparing the [CII] emission to UV attenuation, dust emission, PAH, and CO emission in different regions of the galaxy, we find a clear excess of [CII] emission along the impact front with the intra-group medium. We estimate that the shock due to the impact with the intra-group medium increases the [CII] emission along the shock front by 60% and the global [CII] emission by approximately 25% with respect to the predicted [CII] emission assuming only excitation caused by stellar radiation. This result shows the danger of interpreting [CII] emission as directly related to star formation since shocks and other mechanisms can significantly contribute to the total [CII] emission from galaxies in groups and clusters.

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Dario Fadda, Jessica S. Sutter, Robert Minchin, Fiorella Polles. 2023-10-03. Shock enhanced [CII] emission from the infalling galaxy Arp 25. https://arxiv.org/abs/2310.02358

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