INVESTIGATING THE PRESENCE OF 500 μm SUBMILLIMETER EXCESS EMISSION IN LOCAL STAR FORMING GALAXIES

Submillimeter excess emission has been reported at 500 mu m in a handful of local galaxies, and previous studies suggest that it could be correlated with metal abundance. We investigate the presence of an excess submillimeter emission at 500 mu m for a sample of 20 galaxies from the Key Insights on Nearby Galaxies: a Far Infrared Survey with Herschel (KINGFISH) that span a range of morphologies and metallicities (12 + log(O/H) = 7.8-8.7). We probe the far-infrared (IR) emission using images from the Spitzer Space Telescope and Herschel Space Observatory in the wavelength range 24-500 mu m. We model the far-IR peak of the dust emission with a two-temperature modified blackbody and measure excess of the 500 mu m photometry relative to that predicted by our model. We compare the submillimeter excess, where present, with global galaxy metallicity and, where available, resolved metallicity measurements. We do not find any correlation between the 500 mu m excess and metallicity. A few individual sources do show excess (10%-20%) at 500 mu m; conversely, for other sources, the model overpredicts the measured 500 mu m flux density by as much as 20%, creating a 500 mu m "deficit." None of our sources has an excess larger than the calculated 1 sigma uncertainty, leading us to conclude that there is no substantial excess at submillimeter wavelengths at or shorter than 500 mu m in our sample. Our results differ from previous studies detecting 500 mu m excess in KINGFISH galaxies largely due to new, improved photometry used in this study.