Comparing galaxy disk and star-formation properties in X-ray bright and
  faint groups and clusters
  Galaxy morphologies and star-formation rates depend on environment. Galaxies
in under-dense regions are generally star-forming and disky whereas galaxies in
overdense regions tend to be early-type and not actively forming stars. The
mechanism(s) responsible for star-formation quenching and morphological
transformation remain unclear, although many processes have been proposed. We
study the dependence of star-formation and morphology on X-ray luminosity for
galaxies in Sloan Digital Sky Survey Data Release 7 (SDSS-DR7) groups and
clusters. While controlling for stellar and halo mass dependencies, we find
that galaxies in X-ray strong groups and clusters have preferentially low
star-forming and disk fractions -- with the differences being strongest at low
stellar masses. The trends that we observe do not change when considering only
galaxies found within or outside of the X-ray radius of the host group. When
considering central and satellite galaxies separately we find that this
dependence on X-ray luminosity is only present for satellites, and we show that
our results are consistent with "galaxy stangulation" as a mechanism for
quenching these satellites. We investigate the dynamics of the groups and
clusters in the sample, and find that the velocity distributions of galaxies
beyond the virial radius in low X-ray luminosity halos tend to be less Gaussian
in nature than the rest of the data set. This may be indicative of low X-ray
luminosity groups and clusters having enhanced populations of star-forming and
disk galaxies as a result of recent accretion.
