On the Origin of Gas-poor Galaxies in Galaxy Clusters Using Cosmological Hydrodynamic Simulations

Abstract

The environmental effect is commonly used to explain the excess of gas-poor galaxies in galaxy clusters. Meanwhile, the presence of gas-poor galaxies at cluster outskirts, where galaxies have not spent enough time to feel the cluster environmental effect, hints at the presence of preprocessing. Using cosmological hydrodynamic simulations on 16 clusters, we investigate the mechanisms of gas depletion of galaxies found inside clusters. The gas-depletion mechanisms can be categorized into three channels based on where and when they took place. First, 34% of our galaxies are gas poor before entering clusters (“preprocessing”). They are mainly satellites that have undergone the environmental effect inside group halos. Second, 43% of the sample quickly became gas deficient in clusters before the first pericentric pass (“fast cluster processing”). Some of them were group satellites that are low in gas at the time of cluster entry compared to the galaxies directly coming from the field. Even the galaxies with large gas fractions take this channel if they fall into massive clusters (≳1014.5 M ⊙) or approach cluster centers through radial orbits. Third, 24% of our sample retain gas even after their first pericentric pass (“slow cluster processing”) as they fall into the less massive clusters or have circular orbits. The relative importance of each channel varies with a cluster’s mass, while the exact degree of significance is subject to large uncertainties. Group preprocessing accounts for one-third of the total gas depletion, but it also determines the gas fraction of galaxies at their cluster entry, which in turn determines whether a galaxy should take the fast or slow cluster processing.

The Roles of Mass and Environment in the Quenching of Galaxies. II.

“…According to our analysis, the main conclusion was that mass quenching dominates at any redshift, while the environment plays only a marginal role. We stated that all the results could have been put together logically if environmental processes act very fast (Jung et al 2018) in a way that they do not affect the star formation activity, but can increase the probability of galaxies to become quiescent. In the last decade many authors have studied mass and environmental quenching by looking at their efficiencies (with all the caveats discussed above).…”

YZiCS: Unveiling the Quenching History of Cluster Galaxies Using Phase-space Analysis

“…On the one hand, more massive galaxies can better resist the direct gas stripping process (e.g., ram-pressure) thanks to their stronger gravitational restoring force (e.g., Pasquali et al 2019;Smith et al 2019). On the other hand, more massive galaxies tend to be more (partially) self-quenched even before en-tering clusters, which makes the ram pressure stripping more effective (Jung et al 2018).…”

“…According to previous simulation studies (e.g., Gill et al 2005;Oman et al 2013;Rhee et al 2017), cluster galaxies, during their infall into a cluster, tend to follow a common path through this phase space (see Figure 1 in Rhee et al 2017, for a summary). This premise is supported by the fact that infalling galaxies share favored orbital parameters (Wetzel 2011) and the crossing times of clusters are similar regardless of cluster mass and stellar mass (Jung et al 2018;Lotz et al 2018).…”

The H i mass function of group galaxies in the ALFALFA survey

“…There is now a considerable body of evidence, both from simulations (Bahé & McCarthy 2015;Marasco et al 2016;Jung et al 2018) and observations (Hess & Wilcots 2013;Dénes et al 2016;Jaffé et al 2016;Odekon et al 2016;Brown et al 2017), indicating that galaxies are "preprocessed" in groups, depleting their HI content and sup-pressing their star formation rate, before they fall into clusters. Hence the difference between the HIMF found in groups and in wide-field surveys is not entirely unexpected as the H i-rich galaxies typically detected by blind 21 cm surveys are mostly thought to be field galaxies in their own distinct halos (e.g.…”