The pre-processing of subhaloes in SDSS groups and clusters

TL;DR

This study examines how pre-processing in subhaloes influences galaxy quenching in SDSS groups and clusters, revealing that pre-processing significantly affects galaxy quiescence mainly in the most massive systems.

Contribution

It introduces a method to identify subhaloes and demonstrates the role of pre-processing in galaxy quenching within massive galaxy clusters.

Findings

Higher subhalo fractions in more massive systems.

Enhanced quiescent fraction in subhaloes at large radii.

Pre-processing impacts galaxy quenching mainly in halos > 10^14.5 M_sun.

Abstract

We investigate pre-processing using the observed quenched fraction of group and cluster galaxies in the Yang et al. (2007) SDSS-DR7 group catalogue in the redshift range of 0.01 < z < 0.045. We categorize group galaxies as virialized, infall or backsplash and we apply a combination of the Dressler-Shectman statistic and group member velocities to identify subhaloes. On average the fraction of galaxies that reside in subhaloes is a function of host halo mass, where more massive systems have a higher fraction of subhalo galaxies both in the overall galaxy and infall populations. Additionally, we find that between 2 < r_200 < 3 the quiescent fraction is higher in the subhalo population with respect to both the field and non-subhalo populations. At these large radii (2 < r_200 < 3), the majority of galaxies (~ 80 %) belong to the infall population and therefore, we attribute the enhanced quenching to infalling subhalo galaxies, indicating that pre-processing has occurred in the subhalo population. We conclude that pre-processing plays a significant role in the observed quiescent fraction, but only for the most massive (M_halo > 10^14.5 M_sun) systems in our sample.