Using [C ii] 158 μm Emission from Isolated ISM Phases as a Star Formation Rate Indicator

Abstract

The brightest observed emission line in many star-forming galaxies is the  158  μ m line, making it detectable up to z  ∼ 7. In order to better understand and quantify the emission as a tracer of star formation, the theoretical ratio between the  205  μ m emission and the  158  μ m emission has been employed to empirically determine the fraction of emission that originates from the ionized and neutral phases of the interstellar medium (ISM). Sub-kiloparsec measurements of the  158  μ m and  205  μ m lines in nearby galaxies have recently become available as part of the Key Insights in Nearby Galaxies: a Far Infrared Survey with Herschel (KINGFISH) and Beyond the Peak programs. With the information from these two far-infrared lines along with the multi-wavelength suite of KINGFISH data, a calibration of the emission line as a star formation rate (SFR) indicator and a better understanding of the deficit are pursued. emission is also compared to polycyclic aromatic hydrocarbon (PAH) emission in these regions to compare photoelectric heating from PAH molecules to cooling by in the neutral and ionized phases of the ISM. We find that the emission originating in the neutral phase of the ISM does not exhibit a deficit with respect to the infrared luminosity and is therefore preferred over the emission originating in the ionized phase of the ISM as an SFR indicator for the normal star-forming galaxies included in this sample.