Nonparametric galaxy morphology from UV to submm wavelengths

Abstract

We present the first nonparametric morphological analysis of a set of spiral galaxies from UV to submillimeter (submm) wavelengths. Our study is based on high-quality multi-wavelength imaging for nine well-resolved spiral galaxies from the DustPedia database, combined with nonparametric morphology indicators calculated in a consistent way using the StatMorph package. We measure the half-light radius, the concentration index, the asymmetry index, the smoothness index, the Gini coefficient, and the M20 indicator in various wavebands from UV to submm wavelengths, and in stellar mass, dust mass, and star formation rate maps. We find that the interstellar dust in galaxies is distributed in a more extended, less centrally concentrated, more asymmetric, and more clumpy way than the stars are. This is particularly evident when comparing morphological indicators based on the stellar mass and dust mass maps. This should serve as a warning sign against treating the dust in galaxies as a simple smooth component. We argue that the nonparametric galaxy morphology of galaxies from UV to submm wavelengths is an interesting test for cosmological hydrodynamics simulations.