Baryon content of massive galaxy clusters at 0.57 < z < 1.33

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 = 6 × 10¹⁴ M_⊙. 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_{star }^{BCG} constitutes 0.12 ± 0.01 per cent of the halo mass for a 6 × 10¹⁴ M_⊙ 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 ± 0.1} M_⊙, 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_⋆, the ICM fraction f_ICM, the collapsed baryon fraction f_c and the baryon fraction f_b. At a pivot mass of 6 × 10¹⁴ M_⊙ and redshift z = 0.9, the characteristic values are f_⋆ = 1.1 ± 0.1 per cent, f_ICM = 9.6 ± 0.5 per cent, f_c = 10.7 ± 1.1 per cent and f_b = 10.7 ± 0.6 per cent. These fractions all vary with cluster mass at high significance, with higher mass clusters having lower f_⋆ and f_c and higher f_ICM and f_b. When accounting for a 15 per cent 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_⋆, lower f_ICM) and the field (lower f_⋆, higher f_ICM), balancing to keep f_⋆ and f_ICM approximately constant since z ∼ 0.9.