CLASH-VLT: The stellar mass function and stellar mass density profile of the z = 0.44 cluster of galaxies MACS J1206.2-0847

Abstract

Context. The study of the galaxy stellar mass function (SMF) in relation to the galaxy environment and the stellar mass density profile, (r), is a powerful tool to constrain models of galaxy evolution. Aims. We determine the SMF of the z = 0.44 cluster of galaxies MACS J1206.2-0847 separately for passive and star-forming (SF) galaxies, in different regions of the cluster, from the center out to approximately 2 virial radii. We also determine (r) to compare it to the number density and total mass density profiles. Methods. We use the dataset from the CLASH-VLT survey. Stellar masses are obtained by spectral energy distribution fitting with the MAGPHYS technique on 5-band photometric data obtained at the Subaru telescope. We identify 1363 cluster members down to a stellar mass of 109.5 M, selected on the basis of their spectroscopic (~1/3 of the total) and photometric redshifts. We correct our sample for incompleteness and contamination by non members. Cluster member environments are defined using either the clustercentric radius or the local galaxy number density. Results. The whole cluster SMF is well fitted by a double Schechter function, which is the sum of the two Schechter functions that provide good fits to the SMFs of, separately, the passive and SF cluster populations. The SMF of SF galaxies is significantly steeper than the SMF of passive galaxies at the faint end. The SMF of the SF cluster galaxies does not depend on the environment. The SMF of the passive cluster galaxies has a significantly smaller slope (in absolute value) in the innermost (= 0.50 Mpc, i.e., ~0.25 virial radii), and in the highest density cluster region than in more external, lower density regions. The number ratio of giant/subgiant galaxies is maximum in this innermost region and minimum in the adjacent region, but then gently increases again toward the clusteroutskirts. This is also reflected in a decreasing radial trend of the average stellar mass per cluster galaxy. On the other hand, the stellar mass fraction, i.e., the ratio of stellar to total cluster mass, does not show any significant radial trend. Conclusions. Our results appear consistent with a scenario in which SF galaxies evolve into passive galaxies due to density-dependent environmental processes and eventually get destroyed very near the cluster center to become part of a diffuse intracluster medium. Dynamical friction, on the other hand, does not seem to play an important role. Future investigations of other clusters of the CLASH-VLT sample will allow us to confirm our interpretation.