Galaxy Properties Across Diverse Halo Environments

Abstract

Correlations between galaxy properties and environment have been observed in many environments, showing that red, quiescent, early-type galaxies are found preferentially in dense regimes. This thesis uses a large sample of SDSS group galaxies to further probe these environmental dependences, with a focus on determining the properties of galaxies across different halo environments. We first investigate the mass segregation of galaxies in haloes of groups covering a wide range of masses. We find significant mass segregation in low-mass groups with the strength of mass segregation decreasing with increasing halo mass – to the point where high-mass clusters show no detectable mass segregation. We also find that mass segregation trends are more prominent when including lower mass galaxies. Similar trends are observed when considering the fraction of massive galaxies as a function of radius as opposed to mean galaxy mass. Secondly, we study the star formation and morphology of satellite galaxies in different halo environments. Specifically, we probe beyond the well established correlations with stellar and halo mass and investigate the dependence of star-forming and disc fractions on group X-ray luminosity. We show that galaxies in X-ray underluminous groups have enhanced star-forming and disc fractions, for a given stellar and halo mass. These observations contribute to the understanding and interpretation of the environmental dependence of galaxy properties by providing a framework with which the lack of consensus regarding the presence of mass segregation in groups and clusters can potentially be reconciled, as well as quantifying new correlations with X-ray luminosity beyond the established dependences on halo mass.