The mass density profile and star formation history of Gaussian and non-Gaussian clusters

Abstract

ABSTRACT This paper is the third of a series in which we investigate the discrimination between Gaussian (G) and Non-Gaussian (NG) clusters, based on the velocity distribution of the member galaxies. We study a sample of 177 groups from the Yang catalog in the redshift interval of 0.03 ≤ z ≤ 0.1 and masses ${\ge }10^{14}\, \rm M_{\odot }$. Examining the projected stellar mass density distributions of G and NG groups, we find strong evidence of a higher infall rate in the outskirts of NG groups over the G ones. There is a 61 per cent excess of faint galaxies in NGs when contrasted with G groups, when integrating $\rm from \, 0.8 \,to\, 2.0R/R_{200}$. The study of the star formation history (SFH) of ellipticals and spirals in the three main regions of the projected phase space reveals also that the star formation in faint spirals of NG groups is significantly different from their counterpart in the G groups. The assembled mass for faint spirals varies from 59 per cent at 12.7 Gyr to 75 per cent at 8.0 Gyr, while in G systems this variation is from 82 per cent to 91 per cent. This finding may also be interpreted as a higher infall rate of gas-rich systems in NG groups. This accretion process through the filaments, disturbing the velocity distribution and modifying not only the stellar population of the incoming galaxies but also their SFH, should be seriously considered in modelling galaxy evolution.