Environmental Factors in Measurements of the [CII] Deficit
Jessica Sutter (SOFIA Science Center - California, USA)
Tuesday 12/04/2022 @ 14:00, Remote talk
The 158 micron emission line of singly ionized carbon ([CII]) has become a frequent choice for studies of the most distant galaxies. The long wavelength of this far-infrared fine structure line allows for passage through gas and dust with minimal attenuation and its ability to cool both the neutral and ionized phases of the ISM often make it the brightest observed emission line in star-forming galaxies. This has led to proposals to use [CII] emission as a tracer of a variety of phenomena, including as a star-formation rate (SFR) indicator. One unresolved issue with using [CII] line measurements to trace SFR is the effect known as the [CII] deficit, in which galaxies with increased star formation often see a drop in the ratio of [CII]-to infrared luminosity. This suggests that star-bursting galaxies are producing less [CII] emission than expected, and could cause [CII] measurements of SFR to be underpredicted in these systems. In order to overcome this obstacle and find the best uses for the slew of high-z [CII] detections, it is essential a complete understanding of the cause of this deficit is determined. In pursuit of this goal, observations of [CII] along with a full suite of panchromatic data from 28 nearby galaxies has been put to use. Based on ISM-phase isolated measurements, it appears the thermalization of the [CII] line in the ionized phases of the ISM is a major cause of the observed [CII] deficit.