Galaxy Cluster A 2142: Halo Boundary, “Red Sequence”, Properties of Galaxies Based on SDSS

Abstract—Here we present results of studying the dynamics of galaxies, properties of early-type galaxies, properties of galaxies with the quenched star formation (QGs) in the A 2142 cluster based on the archival data from the Sloan Digital Sky Survey Data (SDSS DR10). We found the observed halo boundary, the “splashback” radius ${{R}_{{{\text{sp}}}}}$, which is equal to 4.12 Mpc (${{M}_{r}} < - {{20.}^{{\text{m}}}}3$) and 4.06 Mpc (${{M}_{r}} < - {{21.}^{{\text{m}}}}5$) over the integral distribution of the number of galaxies as a function of the squared distance from the center. We have studied how early-type galaxies are distributed in the center and in the outskirts of the cluster (${R \mathord{\left/ {\vphantom {R {{{R}_{{200}}}}}} \right. \kern-0em} {{{R}_{{200}}}}}$< 3, ${{M}_{r}} < - {{20.}^{{\text{m}}}}3$) and plotted the “red sequence” in the form of $(g - r) = ( - 0.024 \pm 0.001){{M}_{r}} + (0.441 \pm 0.005)$. Among all the cluster galaxies, the galaxies with the quenched star formation ($- 12$ yr$^{{ - 1}} < \log sSFR < 10.75$ yr$^{{ - 1}}$) make up about one third. We have found that the fraction of QGs beyond the “splashback” radius ${{R}_{{{\text{s}}p}}}$ is the same as in the field at the same $z$ with coordinates of the center of ${\text{16}}{{{\text{.}}}^{{\text{h}}}}{\text{5,}}\,\,31$° and a size of 300′. For galaxies with the stellar masses $\log {{{{M}_{*}}} \mathord{\left/ {\vphantom {{{{M}_{*}}} {{{M}_{ \odot }}}}} \right. \kern-0em} {{{M}_{ \odot }}}} = [10.5;11.0]$ (this is the main mass range of QGs), when entering the cluster, there is a decrease in the radii ${{R}_{{90,r}}}$ by about $30\%$ when moving towards the center.