BUDHIES III: The fate of HI and the quenching of galaxies in evolving
  environments
  In a hierarchical Universe clusters grow via the accretion of galaxies from
the field, groups and even other clusters. As this happens, galaxies can lose
their gas reservoirs via different mechanisms, eventually quenching their
star-formation. We explore the diverse environmental histories of galaxies
through a multi-wavelength study of the combined effect of ram-pressure
stripping and group "processing" in Abell 963, a massive growing cluster at
$z=0.2$ from the Blind Ultra Deep HI Environmental Survey (BUDHIES). We
incorporate hundreds of new optical redshifts (giving a total of 566 cluster
members), as well as Subaru and XMM-Newton data from LoCuSS, to identify
substructures and evaluate galaxy morphology, star-formation activity, and HI
content (via HI deficiencies and stacking) out to $3\times R_{200}$. We find
that Abell 963 is being fed by at least 7 groups, that contribute to the large
number of passive galaxies outside the cluster core. More massive groups have a
higher fraction of passive and HI-poor galaxies, while low-mass groups host
younger (often interacting) galaxies. For cluster galaxies not associated with
groups we corroborate our previous finding that HI gas (if any) is
significantly stripped via ram-pressure during their first passage through the
intra-cluster medium, and find mild evidence for a starburst associated with
this event. In addition, we find an overabundance of morphologically peculiar
and/or star-forming galaxies near the cluster core. We speculate that these
arise as groups pass through the cluster (post-processing). Our study
highlights the importance of environmental quenching and the complexity added
by evolving environments.
