The galaxy stellar mass function of X-ray detected groups

Abstract

We study the stellar mass distribution for galaxies in 160 X-ray detected groups of 10 13 < Log(M 200 /M ) < 2 × 10 14 and compare it with that of galaxies in the field to investigate the action of environment on the build-up of the stellar mass. We highlight differences in the build-up of the passive population in the field, which imprint features in the distribution of stellar mass of passive galaxies at Log(M/M ) < 10.5. The gradual diminishing of the effect when moving to groups of increasing total masses indicates that the growing influence of the environment in bound structures is responsible for the build-up of a quenched component at Log(M/M ) < 10.5. Differently, the stellar mass distribution of star-forming galaxies is similar in shape in all environments, and can be described by a single Schechter function both in groups and in the field. Little evolution is seen up to redshift 1. Nevertheless at z = 0.2-0.4 groups with M 200 < 6 × 10 13 M (low-mass groups) tend to have a characteristic mass for star-forming galaxies that is 50% higher than in higher mass groups; we interpret it as a reduced action of environmental processes in these systems. Furthermore, we analyse the distribution of sSFR-Log(M) in groups and in the field, and find that groups show on average a lower sSFR (by ∼0.2 dex) at z < 0.8. Accordingly, we find that the fraction of star-forming galaxies is increasing with redshift in all environments, but at a faster pace in the denser ones. Finally, our analysis highlights that low-mass groups have a higher fraction (by 50%) of the stellar mass locked in star-forming galaxies than higher mass systems (i.e. 2/3 of their stellar mass).

The evolution of star formation activity in galaxy groups

“…Similarly, we do not observe evolution in the relation between the total stellar mass in groups and the total mass, in agreement with the results of Giodini et al (2012) (see the bottom panel of Fig. 10 and the right-hand panel of Fig.…”

“…According to Peng et al (2010) massive galaxies, as the ones considered in our sample, evolve mostly because of an internally driven process, called 'mass quenching', caused perhaps by feedback from active galactic nuclei. But since this process is unlikely to be more efficient in quenching SF of massive galaxies in massive haloes than in other environments as the stellar mass functions do not change significantly in groups with respect to field (Giodini et al 2012), the 'environmental quenching' must be the main mechanism for quenching the SF of the most massive satellites in massive haloes. Which kind of process is causing this 'environmental quenching' is still quite unknown.…”

Evolution of the galaxy luminosity function in progenitors of fossil groups

“…Several earlier studies attempted to show similarities between LFs in different environments, suggesting the LF as universal function (e.g., Oemler 1974; Gaidos 1997;Colless 1989;De Propris et al 2003). In contrast, a number of studies disagree with the universal shape of LF (e.g., Godwin & Peach 1977;de Filippis et al 2011;Hansen et al 2005;Giodini et al 2012). The luminosity evolution of the bright end and slope of the faint end of the galaxy LF in the field and clusters has been well understood (Bowler et al 2014;Lilly et al 1995;Norberg et al 2002;Willmer et al 2006;Ellis et al 1996;Alshino et al 2010).…”

The environmental dependence of the stellar mass function atz~ 1

“…Some studies have attempted to measure the SMF as a function of local environment at 0.4 z 1.2 (e.g. Bundy et al 2006;Bolzonella et al 2010;Vulcani et al 2011Vulcani et al , 2012Giodini et al 2012). A measurement of the SMF at the highest densities has not yet been achieved in this redshift range.…”