Galaxies in dense cluster environments

Abstract

Galaxy clusters represent some of the most extreme environments in the Universe. They are ideal locations to study the impact of an extreme environment on stellar evolution. In this work, we try to determine how the stellar mass function depends on factors such as the surrounding environments, whether they reside in isolated fields, galaxy groups, or clusters. We use the 9-band photometric galaxy data of the G9 patch from the Kilo Degree Survey (optical) and the VISTA Kilo-Degree Infrared Galaxy Survey (infrared), containing around 3.7 million galaxies, overlapping with the cluster catalog provided by the eROSITA Final Equatorial Depth Surveys (eFEDS). After applying appropriate selection criteria, we have 105 eFEDS clusters within the redshift range 0.385-0.8, covering → 46 square degrees. The large, continuous overlap of the surveys allows us to examine the SMF of the cluster galaxies within the cluster-centric radial bins up to 5R500. We find a clear detection of the cluster galaxy SMF up to 2R500 beyond which it’s consistent with the background. We divide the cluster sample into redshift, mass, and luminosity bins to examine their impact on the SMF. The SMF of cluster galaxies for the high-mass clusters shows a decline at low stellar masses (M→ ↭ 2 ↑ 1010M↑) within 0 ↓ 0.5R500, as compared to a flat SMF for the low-mass clusters, suggesting the low-mass galaxies grow over time before reaching the cluster center. Additionally, we find a higher SMF for the low redshift bin within 0.5R500 at stellar masses M→ < 1010M↑. We also examined the effect of cluster ellipticity on the cluster galaxy SMF and found a higher SMF for low ellipticity clusters within 0.5R500, suggesting a link between the dynamical age and the stellar population growth in the cluster cores.