Μ M Emission as a Star Formation Tracer

The [CII] 157.74 μm transition is the dominant coolant of the neutral interstellar gas, and has great potential as a star formation rate (SFR) tracer. Using the Herschel KINGFISH sample of 46 nearby galaxies, we investigate the relation of [CII] surface brightness and luminosity with SFR. We conclude that [CII] can be used for measurements of SFR on both global and kiloparsec scales in normal star-forming galaxies in the absence of strong active galactic nuclei (AGN). The uncertainty of the Σ[CII] −ΣSFR calibration is ±0.21 dex. The main source of scatter in the correlation is associated with regions that exhibit warm IR colors, and we provide an adjustment based on IR color that reduces the scatter. We show that the color-adjusted Σ[CII] −ΣSFR correlation is valid over almost 5 orders of magnitude in ΣSFR, holding for both normal star-forming galaxies and non-AGN luminous infrared galaxies. Using [CII] luminosity instead of surface brightness to estimate SFR suffers from worse systematics, frequently underpredicting SFR in luminous infrared galaxies even after IR color adjustment (although this depends on the SFR measure employed). We suspect that surface brightness relations are better behaved than the luminosity relations because the former are more closely related to the local far-UV field strength, most likely the main parameter controlling the efficiency of the conversion of far-UV radiation into gas heating. A simple model based on Starburst99 populationsynthesis code to connect SFR to [CII] finds that heating efficiencies are 1%− 3% in normal galaxies. Subject headings: galaxies: star formation — galaxies: ISM — ISM: structure — infrared: galaxies 1 Department of Astronomy, University of Maryland, College Park, MD 20742, USA. 2 Laboratory for Millimeter-wave Astronomy, University of Maryland, College Park, MD 20742, USA 3 Department of Physics and Astronomy, University of Toledo, 2801 West Bancroft Street, Toledo, OH 43606, USA 4 Department of Astronomy, The Ohio State University, 4051 McPherson Laboratory, 140 West 18th Avenue, Columbus, OH 43210, USA 5 Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK 6 Department of Astronomy, University of Massachusetts, Amherst, MA 01003, USA 7 Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125, USA 8 Max-Planck-Institut für Astronomie, Königstuhl 17, D69117 Heidelberg, Germany 9 National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903, USA 10 Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544, USA 11 Leiden Observatory, Leiden University, P.O. Box 9513, 2300-RA Leiden, The Netherlands 12 Spitzer Science Center, California Institute of Technology, MC 314-6, Pasadena, CA 91125, USA 13 Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721, USA 14 Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071, USA 15 Institut d’Astrophysique Spatiale, CNRS (UMR8617) Université Paris-Sud 11, Batiment 121, Orsay, France 16 INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze, Italy 17 European Southern Observatory, Karl Schwarzschild Str. 2, 85748 Garching, Germany 18 NASA Herschel Science Center, IPAC, California Institute of Technology, Pasadena, CA 91125, USA 19 Institut d’Astrophysique de Paris, Université Pierre et Marie Curie, CNRS UMR 7095, 75014 Paris, France 20 Steward Observatory, University of Arizona, Tucson, AZ 85721, USA 21 Raytheon Company, 1151 East Hermans Road, Tucson, AZ 85756, USA ⋆ Deceased January 8, 2014 22 Observatoire de Paris, 61 avenue de l’Observatoire, Paris F-75014, France 2 Herrera-Camus et al.