2018ApJ...853..128V

We analyze the application of star formation rate calibrations using Hα and 22 µm infrared (IR) imaging data in predicting the thermal radio component for a test sample of three edge-on galaxies (NGC 891, NGC 3044, and NGC 4631) in the Continuum Halos in Nearby Galaxies-an EVLA Survey (CHANG-ES). We use a mixture of Hα and 24 µm calibration from Calzetti et al. and a linear 22 µm only calibration from Jarrett et al. on the test sample. We apply these relations on a pixel-to-pixel basis to create thermal prediction maps in the two CHANG-ES bands: L and C band (1.5 GHz and 6.0 GHz, respectively). We analyze the resulting nonthermal spectral index maps, and find a characteristic steepening of the nonthermal spectral index with vertical distance from the disk after application of all methods. We find possible evidence of extinction in the 22 µm data as compared to 70 µm Spitzer Multiband Imaging Photometer imaging in NGC 891. We analyze a larger sample of edge-on and face-on galaxy 25-100 µm flux ratios, and find that the ratios for edge-ons are systematically lower by a factor of 1.36, a result we attribute to excess extinction in the mid-IR in edge-ons. We introduce a new calibration for correcting the Hα luminosity for dust when galaxies are edge-on or very dusty.