Using Concentration Offset to Analyze the Dependence of Galaxy Quenching on Morphology

Abstract

Quenching is the process by which a galaxy's star formation ceases and it moves from being a blue star-forming to a red quiescent galaxy. Concentration has been shown to be a good indicator of this process; this paper uses ΔΣ1 (a concentration offset derived below) to observe how quenching differs between galaxy morphologies. We use Sloan Digital Sky Survey data to plot ΔSFR against ΔΣ1, with morphological classifications from Galaxy Zoo 2 and environmental classifications from Yang et al. We find a difference in the distributions of concentration offset between early- and late-types that is not observed with differing environmental conditions and so conclude that separating the two allows more insight into their individual quenching processes. Late-types are shown to follow a process of compaction before then quenching and this is consistent with a picture where they quench slower than the early-types.