Connecting galaxy structure and star formation: the role of environment in formation of S0 galaxies

Abstract

In this work, we investigate the reason behind the increased occurrence of S0 galaxies in high-density environments. Our sample comprises of ∼2500 spiral and ∼2000 S0 galaxies spanning a wide range of environments. Dividing the galaxies into categories of classical and pseudo-bulge hosting spiral and S0 galaxies, we have studied their properties as a function of the environment. We find that the fraction of pseudo-bulge hosting disc galaxies decreases with increase in density. The classical bulge hosting spirals and S0 galaxies follow a similar trend in less dense environments but towards higher densities, we observe an increase in the fraction of classical bulge host S0 galaxies at the expense of spirals. Comparing the structural and the star formation properties of galaxies on the size–mass and NUV − r colour–mass planes, respectively, we infer that classical bulge hosting spirals are likely to get transformed into S0 morphology. We notice a trend of galaxy structure with environment such that the fraction of classical bulge hosting spiral galaxies is found to increase with environment density. We also find that among classical bulge hosting spirals, the fraction of quenched galaxies increases in denser environments. We surmise that the existence of more classical bulge hosting spirals galaxies and more efficient quenching leads to the observed increased occurrence of S0 galaxies in high-density environments. The relation between galaxy structure and environment also exists for the disc galaxies irrespective of their visual morphology, which is driven mainly by halo mass.