Phase-space Analysis in the Group and Cluster Environment: Time Since Infall and Tidal Mass Loss

Abstract

Using the latest cosmological hydrodynamic N-body simulations of groups and clusters, we study how location in phase-space coordinates at z=0 can provide information on environmental effects acting in clusters. We confirm the results of previous authors showing that galaxies tend to follow a typical path in phase-space as they settle into the cluster potential. As such, different regions of phase-space can be associated with different times since first infalling into the cluster. However, in addition, we see a clear trend between total mass loss due to cluster tides, and time since infall. Thus we find location in phase-space provides information on both infall time, and tidal mass loss. We find the predictive power of phase-space diagrams remains even when projected quantities are used (i.e. line-of-sight velocities, and projected distances from the cluster). We provide figures that can be directly compared with observed samples of cluster galaxies and we also provide the data used to make them as supplementary data, in order to encourage the use of phase-space diagrams as a tool to understand cluster environmental effects. We find that our results depend very weakly on galaxy mass or host mass, so the predictions in our phase-space diagrams can be applied to groups or clusters alike, or to galaxy populations from dwarfs up to giants.

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

“…A phase-space diagram is a plot of velocity versus distance of cluster galaxies, which are both measured with respect to the cluster's center. 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).…”

“…We will refer to them as "YZiCS clusters" and "YZiCS galaxies", respectively. All clusters range in virial mass from 5 × 10 13 M to 1 × 10 15 M , and more detailed information about the individual clusters is given in Table 1 of Rhee et al (2017). To identify DM halos and galaxies in each snapshot, we used the HaloMaker and the GalaxyMaker codes, respectively, based on the AdaptaHOP method (Aubert et al 2004;Tweed et al 2009).…”

GASP XXIV. The History of Abruptly Quenched Galaxies in Clusters

“…It might therefore be either a pre-processed galaxy or an ancient infaller, rather than a recent infaller. Rhee et al (2017) have indeed shown that ∼ 40% of galaxies in this area are ancient contaminants to the recent infaller population. A500 22 184 and A3158 B 0234 are very close to the edge of the typical region delimited by the escape velocity in relaxed systems, and given their spectral properties they are consistent with being recent infallers that suffer a truncation of the star formation as a consequence of their first encounter with the harsh cluster environment.…”

“…According to cosmological simulations (Haines et al 2015;Rhee et al 2017), galaxies that have been in a cluster for a very long time have lower velocities and clustercentric radii because they have had enough time to sink into the potential well of the cluster. On the other hand, infalling galaxies approach the cluster core with high relative velocities at all clustercentric distances.…”

“…The other galaxies are located inside the typical trumpet-shaped region of the relaxed systems, in an area where both recent and ancient infallers could be actually found (Rhee et al 2017).…”