Abstract:
We analyse the dependence of galaxy evolution on cluster dynamical state and galaxy luminosities for a sample of 146 galaxy clusters from the Yang SDSS DR7 catalogue. Clusters were split according to their velocity distribution in Gaussians (G) and Non-Gaussians (NG) via the Hellinger Distance parameter, and further divided by luminosity regime. We performed a classification by clustering galaxies in the Age-SSFR plane providing three galaxy classes: star-forming (SF), passive (PAS), and an intermediate one (GV -- green valley). Our results indicate that galaxies evolve in the same way in G and NG systems, but they also suggest that the formation history of these systems leads to different mixtures of galactic types and infall patterns. Specifically, we find more bright SF + GV galaxies in NG (55%) than in G systems (43%). We also find more bright passive galaxies in G (57%) than in NG (45%) systems. Separating the GV into star-forming and passive components, we find more bright galaxies in the passive mode of NG (82%) than in G (61%) systems. We also find more intermediate faint galaxies in the star-forming component of NG (78%) than in G (60%) systems. Our results suggest the GV as the stage of galaxy evolution where the transition from types Sab and Scd to S0 must be taking place, but the conversion of one morphological type into another is independent of the dynamical stage of the clusters. In addition, from the study of velocity dispersion profiles, we find that objects recently infalling in clusters also have a different composition between G and NG systems, while all galaxy types infall onto G clusters, Sab and Scd dominate the infall onto NG clusters.
