Paper detail

NoSOCS in SDSS. IV. The Role of Environment Beyond the Extent of Galaxy Clusters

We are able to extend the investigation of the color-morphology-density-radius relations, for bright and faint galaxies, to $R \gtrsim 3 \times R_{200}$ and to very low density regions, probing the transition region between cluster and field galaxies, and finding a smooth variation between these two populations. We investigate the environmental variation of galaxy properties (and their relations), such as color, spectral type and concentration. Our sample comprises 6,415 galaxies that were previously selected as cluster members from 152 systems with $z \le 0.100$. Our main findings are: (i) The fraction of discs is generally higher than the ones for blue and star-forming galaxies, indicating a faster transformation of color and star-formation compared to structural parameters. (ii) Regarding the distance to the cluster center we find a small variation in the galaxy populations outside the virial radius. Once within that radius the fractions of each population change fast, decreasing even faster within $R \sim 0.3 \times R_{200}$. (iii) We also find a small increase in the fraction of blue faint galaxies within $R \sim 0.4 \times R_{200}$, before decreasing again to the most central bin. (iv) Our results do not indicate a significant dependence on cluster mass, except for the disc fraction in the core of clusters. (v) The relations between galaxy properties also point to no dependence on cluster mass, except for the scatter of the color stellar mass relation. Our results corroborate a scenario on which pre-processing in groups leads to a strong evolution in galaxy properties, before they are accreted by large clusters (abridged).