ACCESS: NIR Luminosity Function and Stellar Mass Function of Galaxies in the Shapley Supercluster Environment

الأصل · EN

We present the NIR luminosity (LF) and stellar mass functions (SMF) of galaxies in the core of the Shapley supercluster at z=0.048, based on new K-band observations in conjunction with B- and R-band photometry and a subsample of 650 galaxies spectroscopically confirmed supercluster members, allowing to investigate the galaxies down to Mₖ*+6 and M=10⁸.75 Mₛun. For the 3 deg² field the K-band LF is described by a Schechter function with Mₖ*=-24.96+-0.10 and α=-1.42+-0.03. We investigate the effect of environment by deriving the LF in three regions selected according to the local galaxy density, and observe a significant increase in the faint-end slope going from the high- (α=-1.33) to the low-density (α=-1.49) environments. The SMF is fitted well by a Schechter function with log₁0(M*)=11.16+-0.04 and α=-1.20+-0.02. The SMF of supercluster galaxies is also characterised by an excess of massive galaxies that are associated to the cluster BCGs. While the value of M* depends on environment the slope of the galaxy SMF does not vary with the environment. By comparing our findings with cosmological simulations, we conclude that the environmental dependences of the LF are not primary due to variations in the merging histories, but to processes which are not treated in the semi-analytical models, such as tidal stripping or harassment. In field regions the SMF shows a sharp upturn below M=10⁹ Mₛun, close to our mass limit, suggesting that the upturns seen in our K-band LFs, but not in the SMF, are due to this dwarf population. The environmental variations seen in the faint-end of the K-band LF suggests that dwarf galaxies, which are easier to strip than their more massive counterparts, are affected by tidal/gas stripping upon entering the supercluster.