2016MNRAS.455..258C

We study the stellar, brightest cluster galaxy (BCG) and intracluster medium (ICM) masses of 14 South Pole Telescope (SPT) selected galaxy clusters with median redshift z = 0.9 and mass M500 = 6x10¹⁴M_☉. We estimate stellar masses for each cluster and BCG using six photometric bands, the ICM mass using X-ray observations and the virial masses using the SPT Sunyaev-Zel'dovich effect signature. At z = 0.9, the BCG mass M_*^BCG constitutes 0.12±0.01 percent of the halo mass for a 6x10¹⁴M_☉ cluster, and this fraction falls as M_500^-0.58±0.07. The cluster stellar mass function has a characteristic mass M0 = 10^11.0±0.1M_☉, and the number of galaxies per unit mass in clusters is larger than in the field by a factor of 1.65±0.20. We combine our SPT sample with previously published samples at low redshift and correct to a common initial mass function and for systematic virial mass differences. We then explore mass and redshift trends in the stellar fraction f{sstarf}, the ICM fraction fICM, the collapsed baryon fraction fc and the baryon fraction fb. At a pivot mass of 6x10¹⁴M_☉ and redshift z = 0.9, the characteristic values are f{sstarf} = 1.1±0.1 percent, fICM = 9.6±0.5 percent, fc = 10.7±1.1 percent and fb = 10.7±0.6 percent. These fractions all vary with cluster mass at high significance, with higher mass clusters having lower f{sstarf} and fc and higher fICM and fb. When accounting for a 15 percent systematic virial mass uncertainty, there is no statistically significant redshift trend at fixed mass. Our results support the scenario where clusters grow through accretion from subclusters (higher f{sstarf}, lower fICM) and the field (lower f{sstarf}, higher fICM), balancing to keep f{sstarf} and fICM approximately constant since z ∼ 0.9.