Dependence of the bright end of galaxy luminosity function on cluster dynamical state

TL;DR

This study investigates how the luminosity distribution of bright galaxies in clusters depends on the clusters' dynamical states, revealing that relaxed clusters have fainter galaxy populations but brighter central galaxies, supporting hierarchical formation models.

Contribution

It provides the first large-sample analysis of the dependence of the bright end of galaxy luminosity functions on cluster dynamical states using SDSS data.

Findings

Relaxed clusters have a fainter characteristic magnitude (M*)

Relaxed clusters contain fewer bright non-BCG galaxies

Brightest cluster galaxies (BCGs) are brighter in relaxed clusters

Abstract

Luminosity function of cluster galaxies provides a fundamental constraint on galaxy evolution in cluster environments. By using the bright member galaxies of a large sample of rich clusters identified from Sloan Digital Sky Survey, we obtain the bright end of composite luminosity functions of cluster galaxies, and study their dependence on cluster dynamical state. After a redshift-evolution correction of absolute magnitude, the luminosity function of member galaxies can be well fitted by a Schechter function when the brightest cluster galaxies (BCGs) are excluded. The absolute magnitudes of BCGs follow a Gaussian function with a characteristic width of about 0.36 mag. We find that the luminosity function of galaxies in more relaxed clusters has a fainter characteristic absolute magnitude (M_{\ast}), and these clusters have fewer bright non-BCG member galaxies but a brighter BCG. Our results suggest the co-evolution of galaxy population with cluster dynamical state and somewhat support the hierarchical formation scenario of the BCGs.