The Spatially Resolved [CII] Cooling Line Deficit in Galaxies
Abstract
We present [CII] 158um measurements from over 15,000 resolved regions within 54 nearby galaxies of the KINGFISH program to investigate the so-called [CII] "line cooling deficit" long known to occur in galaxies with different luminosities. The [CII]/TIR ratio ranges from above 1% to below 0.1% in the sample, with a mean value of 0.48+-0.21%. We find that the surface density of 24um emission dominates this trend, with [CII]/TIR dropping as nuInu{24um} increases. Deviations from this overall decline are correlated with changes in the gas phase metal abundance, with higher metallicity associated with deeper deficits at a fixed surface brightness. We supplement the local sample with resolved [CII] measurements from nearby luminous infrared galaxies and high redshift sources from z=1.8-6.4, and find that star formation rate density drives a continuous trend of deepening [CII] deficit across six orders of magnitude in SFRD. The tightness of this correlation suggests that an approximate star formation rate density can be estimated directly from global measurements of [CII]/TIR, and a relation is provided to do so. Several low-luminosity AGN hosts in the sample show additional and significant central suppression of [CII]/TIR, but these deficit enhancements occur not in those AGN with the highest X-ray luminosities, but instead those with the highest central starlight intensities. Taken together, these results demonstrate that the [CII] cooling line deficit in galaxies likely arises from local physical phenomena in interstellar gas.
Keywords
Cite
@article{arxiv.1611.01521,
title = {The Spatially Resolved [CII] Cooling Line Deficit in Galaxies},
author = {J. D. T. Smith and Kevin Croxall and Bruce Draine and Ilse De Looze and Karin Sandstrom and Lee Armus and Pedro Beirao and Alberto Bolatto and Mederic Boquien and Bernhard Brandl and Alison Crocker and Daniel A. Dale and Maud Galametz and Brent Groves and George Helou and Rodrigo Herrera-Camus and Leslie Hunt and Robert Kennicutt and Fabian Walter and Mark Wolfire},
journal= {arXiv preprint arXiv:1611.01521},
year = {2016}
}
Comments
17 pages, 5 figures, accepted for publication in ApJ