CLASH-VLT: Substructure in the galaxy cluster MACSJ1206.2-0847 from kinematics of galaxy populations

Aims: In the effort to understand the link between the structure of galaxy clusters and their galaxy populations we focus on MACSJ1206.2-0847 at z ~ 0.44 and probe its substructure in the projectedphase space through the spectrophotometric properties of a large numberof galaxies from the CLASH-VLT survey. Methods: Our analysis ismainly based on an extensive spectroscopic dataset of 445 membergalaxies mostly acquired with VIMOS at VLT as part of our ESO LargeProgramme sampling the cluster out to a radius ~2R_200 (4h_70^-1 Mpc). We classify 412 galaxies as passivewith strong Hδ absorption (red and blue galaxies) and withemission lines from weak to very strong. A number of tests forsubstructure detection are applied to analyze the galaxy distribution inthe velocity space in 2D space and in 3D projected phase-space.Results: Studied in its entirety the cluster appears as a large-scalerelaxed system with a few secondary minor overdensities in 2Ddistribution. We detect no velocity gradients or evidence of deviationsin local mean velocities. The main feature is the WNW-ESE elongation.The analysis of galaxy populations per spectral class highlights a morecomplex scenario. The passive galaxies and red strong Hδ galaxiestrace the cluster center and the WNW-ESE elongated structure. The redstrong Hδ galaxies also mark a secondary dense peak ~2h_70^-1 Mpcat ESE. The emission line galaxiescluster in several loose structures mostly outside R_200. Twoof these structures are also detected through our 3D analysis. Theobservational scenario agrees with MACS J1206.2-0847 having WNW-ESE asthe direction of the main cluster accretion traced by passive galaxiesand red strong Hδ galaxies. The red strong Hδ galaxiesinterpreted as poststarburst galaxies date a likely important event 1-2Gyr before the epoch of observation. The emission line galaxies trace asecondary ongoing infall where groups are accreted along severaldirections