Preprocessing among the Infalling Galaxy Population of EDisCS Clusters

Abstract

We present results from a low-resolution spectroscopic survey for 21 galaxy clusters at 0.4 < z < 0.8 selected from the ESO Distant Cluster Survey (EDisCS). We measured spectra using the Low-Dispersion Prism (LDP) in IMACS on the Magellan Baade telescope and calculate redshifts with a precision of σ z = 0.006. We find 1, 602 galaxies that are brighter than R = 22.6 in the large-scale cluster environs. We identify the galaxies expected to be accreted by the clusters as they evolve to z = 0 using spherical infall models, and find that ∼ 30-70% of the z = 0 cluster population lies outside the virial radius at z ∼ 0.6. For analogous clusters at z = 0, we calculate that the ratio of galaxies that have fallen into the clusters since z ∼ 0.6 to that which were already in the core at that redshift is typically between ∼ 0.3 and 1.5. This wide range of ratios is due to intrinsic scatter and is not a function of velocity dispersion, so a variety of infall histories is to be expected for clusters with current velocity dispersions of 300 < ∼ σ < ∼ 1200 km s −1 . Within the infall regions of z ∼ 0.6 clusters, we find a larger red fraction of galaxies than in the field and greater clustering among red galaxies than blue. We interpret these findings as evidence of "preprocessing", where galaxies in denser local environments have their star formation rates affected prior to their aggregation into massive clusters, although the possibility of backsplash galaxies complicate the interpretation.

The GOGREEN survey: dependence of galaxy properties on halo mass at z &gt; 1 and implications for environmental quenching

“…At fixed stellar mass, the quiescent fraction declines with increasing redshift, and is higher in denser environments. This has been thoroughly demonstrated in works studying dense environments of rich groups and clusters in the local z ∼ 0 Universe (Gómez et al 2003;Balogh et al 2004a;Kauffmann et al 2004;Hou, Parker & Harris 2014), as well as intermediate 0 < z < 1 redshifts (De Lucia et al 2004;Wilman et al 2005;Cooper et al 2006;McGee et al 2011;Giodini et al 2012;van der Burg et al 2018;Just et al 2019) and at z > 1 (Muzzin et al 2012;Balogh et al 2014;Nantais et al 2016;Guglielmo et al 2019;Strazzullo et al 2019;van der Burg et al 2020). At low redshifts, the dependence of the quiescent fraction on stellar mass and environment is largely separable (Baldry et al 2006;Peng et al 2010;Kovač et al 2014;Balogh et al 2016;van der Burg et al 2018).…”

Galaxy and Mass Assembly (GAMA): Demonstrating the Power of WISE in the Study of Galaxy Groups to z < 0.1

“…In addition, it has been suggested that the dominance of earlytype galaxies in rich clusters is the result of galaxies being "pre-processed" in low to medium density environments (Zabludoff & Mulchaey 1998;Fujita 2004) before being assimilated into larger structures (e.g. Bianconi et al 2018;Just et al 2019;Haines et al 2015). Studies examining the infall regions of clusters suggest that preprocessing may be occurring in overdensities (groups) located in filamentary structures, as part of the hierarchical growth of structure (e.g.…”

The Three Hundred project: the gas disruption of infalling objects in cluster environments

“…Determining the extent of galaxy disruption in 'subdominant' environments, such as filaments and group-sized haloes, before an infalling galaxy passes beyond the virial radius of a galaxy cluster, also known as pre-processing (Fujita 2004), is likewise important. Pre-processing has been suggested as a possible cause for recent observational results that find suppressed star formation (Lu et al 2012;Cybulski et al 2014;Haines et al 2015), lower disc fractions (Roberts & Parker 2017), and higher red fractions (Just et al 2019) in infalling galaxies at high cluster-centric radii compared with the field. More specifically, observations have shown that subhaloes, containing satellite galaxies, show signs of pre-processing (Hou, Parker & Harris 2014) at high cluster-centric radii.…”