BUDHIES III: The fate of HI and the quenching of galaxies in evolving environments

TL;DR

This study investigates how galaxy environments, especially in a growing cluster at z=0.2, influence gas loss and star-formation quenching, emphasizing the roles of ram-pressure stripping and group interactions.

Contribution

It provides a detailed multi-wavelength analysis of galaxy environmental histories in Abell 963, highlighting the impact of group accretion and environmental processes on galaxy evolution.

Findings

Abell 963 is fed by at least 7 groups contributing to passive galaxy populations.

More massive groups have higher fractions of passive and HI-poor galaxies.

Ram-pressure stripping significantly affects HI content during first cluster passage.

Abstract

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.