Galaxy Populations in the 26 most massive Galaxy Clusters in the South Pole Telescope SZE Survey

Abstract

We present a study of the optical properties of the 26 most massive galaxy clusters selected within the SPT-SZ 2500 deg${}^2$ survey. This Sunyaev-Zel'dovich effect selected sample spans a redshift range of 0.10 < z < 1.13. We measure the galaxy radial profile, the luminosity function (LF), and the halo occupation number (HON) using optical data with a typical depth of $m^{\ast }$ + 2. The stacked radial profiles are consistent with a NFW profile with a concentration of $2.84_{-0.37}^{+0.40}$ for the red sequence (RS) and $2.36_{-0.35}^{+0.38}$ for the total population. Stacking the data in multiple redshift bins shows a hint of redshift evolution in the concentration when both the total population is used, and when only RS galaxies are used (at 2.1$\ddot{I}ƒ$ and 2.8$\ddot{I}ƒ$, respectively). The stacked LF shows a faint end slope $\hat{I}\pm =-1.06_{-0.03}^{+0.04}$ for the total and $\hat{I}\pm =-0.80_{-0.03}^{+0.04}$ for the RS population. The redshift evolution of $m^{\ast }$ is found to be consistent with a passively evolving Composite Stellar Population (CSP) model. By adopting the CSP model predictions, we explore the redshift evolution of the schechter parameters $\hat{I}\pm$ and $\ddot{I}{•}^{\ast }$. We find $\hat{I}\pm$ for the total population to be consistent with no evolution (0.3$\ddot{I}ƒ$), while evidence of evolution for the red galaxies is mildly significant (1.1-2.1$\ddot{I}ƒ$). The data show that the density $\ddot{I}{•}^{\ast }$/E${}^2$(z) decreases with redshift, in tension with the self-similar expectation at a 2.4$\ddot{I}ƒ$ level for the total population. The measured HON-mass relation has a lower normalization than previous studies at low redshift. Finally, our data support HON redshift evolution at a 2.1$\ddot{I}ƒ$ level, with clusters at higher redshift containing fewer galaxies per unit mass to $m^{\ast }$ + 3 than their low-z counterparts [abridged].

14 pages, 7 figures, 2 tables, submitted to MNRAS, abstract abridged for arXiv submission