A surprising consistency between the far-infrared galaxy luminosity functions of the field and Coma

We present new deep images of the Coma Cluster from the ESA Herschel Space Observatory at wavelengths of 70, 100 and 160 μm, covering an area of 1.75 × 1.0 square degrees encompassing the core and south-west infall region. Our data display an excess of sources at flux densities above 100 mJy compared to blank-field surveys, as expected. We use extensive optical spectroscopy of this region to identify cluster members and hence produce cluster luminosity functions in all three photometric bands. We compare our results to the local field galaxy luminosity function, and the luminosity functions from the Herschel Virgo Cluster Survey. We find consistency between the shapes of the Coma and field galaxy luminosity functions at all three wavelengths; however, we do not find the same level of agreement with that of the Virgo Cluster