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

¹ Dipartimento di Fisica, Univ. degli Studi di Trieste, via Tiepolo 11, 34143 Trieste, Italy
e-mail: annunziatella@oats.inaf.it
² INAF/Osservatorio Astronomico di Trieste, via G. B. Tiepolo 11, 34131, Trieste, Italy
³ INAF/Osservatorio Astronomico di Capodimonte, via Moiariello 16, 80131 Napoli, Italy
⁴ Dipartimento di Fisica e Scienze della Terra, Univ. degli Studi di Ferrara, via Saragat 1, 44122 Ferrara, Italy
⁵ Laboratoire AIM-Paris-Saclay, CEA/DSM-CNRS, Université Paris Diderot, Irfu/Service d’Astrophysique, CEA Saclay, Orme des Merisiers, 91191 Gif-sur-Yvette, France
⁶ Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen, Denmark
⁷ Observatories of the Carnegie Institution of Washington, Pasadena, CA 91 101, USA
⁸ Department of Physics and Astronomy, The Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218, USA
⁹ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
¹⁰ INAF/IAS Milano, via Bassini 15, 20133 Milano, Italy
¹¹ Department of Astronomy, Universidad de Concepción, Casilla 160-C, Concepción, Chile
¹² Dipartimento di Fisica, Università degli Studi di Milano, via Celoria 16, 20133 Milan, Italy
¹³ INFN, Sezione di Trieste, via Valerio 2, 34127 Trieste, Italy
¹⁴ Institute of Astronomy and Astrophysics, Academia Sinica, PO Box 23-141, 10617 Taipei, Taiwan
¹⁵ INAF/Osservatorio Astronomico di Bologna, via Ranzani 1, 40127, Bologna, Italy
¹⁶ Physics and Astronomy Dept., Michigan State University, 567 Wilson Rd., East Lansing, MI 48824, USA
¹⁷ Pontificia Universidad Católica de Chile, Departamento de Astronomía y Astrofísica, Av. Vicuña Mackenna 4860, Santiago, Chile
¹⁸ University of Vienna, Department of Astrophysics, Türkenschanzstr. 17, 1180 Wien, Austria
¹⁹ European Laboratory for Particle Physics (CERN), 1211, Geneva 23, Switzerland

Received: 30 April 2014
Accepted: 7 August 2014

Abstract

Context. The study of the galaxy stellar mass function (SMF) in relation to the galaxy environment and the stellar mass density profile, ρ_⋆(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 ρ_⋆(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 10^9.5 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 cluster outskirts. 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.