Impact of Galaxy Cluster Environment on the Stellar Mass Function of Galaxies

TL;DR

The paper addresses how the dense environment of galaxy clusters shapes the SMF of member galaxies by leveraging the KV450 photometric dataset overlapping with the eFEDS X-ray cluster catalog. It constructs SMFs in cluster-centric radial bins up to $5R_{500}$ for 105 clusters in $0.385<z<0.8$, applying background subtraction and binning by cluster mass and X-ray luminosity. The study finds that cluster SMFs are detectable to $2R_{500}$ with a central peak near $M_*\,\approx\,1-2\times10^{10}\,M_\odot$ and a suppression of the low-mass end in massive clusters, particularly in the inner $0.5R_{500}$, with redshift trends strongest in this inner region; ellipticity-based dynamical-state differences are not statistically robust. Overall, the results demonstrate environment-driven quenching and mass-dependent effects that become most pronounced near cluster centers, providing empirical benchmarks for simulations of cluster galaxy evolution.

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 the evolution of the Stellar Mass Function (SMF), which describes the statistical distribution of galaxies as a function of their stellar masses. In this work, we examine how the SMF of galaxies depends on factors such as the surrounding environments, whether they reside in isolated fields 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 $\sim 46$ 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 $5R_{500}$. We find a clear detection of the cluster galaxy SMF up to $2R_{500}$ beyond which it's consistent with the background. We divide the cluster sample into redshift, mass, and X-ray 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 ($M_*\lesssim 2\times 10^{10}M_\odot$) within $0-0.5R_{500}$, 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 flatter SMF for the low redshift bin within $0.5R_{500}$ at stellar masses $M_*< 10^{10}M_\odot$. We also examined the effect of cluster ellipticity on the cluster galaxy SMF; however do not find statistically significant differences between the high and the low ellipticity clusters.

Figures (8)

• Figure 1: The overlapping sky region between the KV450 galaxy catalog and the eFEDS cluster catalog. The blue-colored region shows the final sample of KV450 galaxies in the G9 patch, and the black circles show eFEDS clusters.
• Figure 2: Total mass (left-hand panel) and redshift (right-hand panel) distribution of eFEDS clusters. The dashed blue line shows all 542 clusters, the solid black line represents the 313 clusters that have KV450 galaxy coverage within $5R_{500}$, and the grey-shaded region shows the final sample of 105 clusters used in SMF analysis within the redshift range (0.385, 0.8).
• Figure 3: The distribution of the total mass for 313 eFEDS clusters (red filled circles) as a function of their redshifts. The final sample of 105 eFEDS clusters used for SMF analysis lies between z = (0.385, 0.8), shown by the dashed vertical lines.
• Figure 4: Left-hand panel: The comparison of the SMF of cluster galaxies in the redshift bins (0.385, 0.5) and (0.5, 0.8) for six cluster-centric radial bins. Middle panel: The SMF comparison for the cluster X-ray luminosity bins ($\rm 10^{43.65}, 10^{44}$) $\rm erg\, s^{-1}$ and ($\rm 10^{44}, 10^{45.1}$) $\rm erg\, s^{-1}$ for the entire redshift range (0.385, 0.8). Right-hand panel: The SMF comparison for the cluster mass bins ($\rm 10^{14.27}, 10^{14.55}$) $M_{\odot}$ and ($\rm 10^{14.55}, 10^{15.08}$) $M_{\odot}$ for the entire redshift range (0.385, 0.8).
• Figure 5: The comparison between the X-ray luminosity and redshift-dependent SMF of cluster galaxies within $0.5R_{500}$ of the cluster-centric radii and the coeval field galaxy SMF calculated within the cluster-centric radial bin $4-5R_{500}$. The top and the bottom panels correspond to low (0.385, 0.5) and high (0.5, 0.8) redshift bins, respectively. The blue triangles and red circles correspond to low ($\log L^{\rm bol}_{\rm 500\, kpc} [\rm erg\, s^{-1}] < 44$) and high ($\log L^{\rm bol}_{\rm 500\, kpc} [\rm erg\, s^{-1}] > 44$) X-ray luminosity bins, respectively, for both redshift bins. The coeval field galaxy SMF is shown by black stars in all the panels.