# Deep spectroscopy of nearby galaxy clusters: II. The Hercules cluster

## TL;DR

This study uses deep spectroscopic data to analyze the galaxy population and dynamical state of the nearby Hercules cluster, revealing its ongoing collapse and the environmental effects on galaxy evolution.

## Contribution

It provides a detailed spectroscopic catalog of cluster members and insights into the evolutionary processes affecting different galaxy populations within the cluster.

## Key findings

- Evidence of the cluster still in its collapsing phase.
- Red galaxy luminosity function shows a deficit of dwarf red galaxies.
- Blue and red galaxy luminosity functions are similar to field populations.

## Abstract

We carried out the deep spectroscopic observations of the nearby cluster A2151 with AF2/WYFFOS@WHT. The caustic technique enables us to identify 360 members brighter than $M_r = -16$ and within 1.3$R_{200}$. We separated the members into subsamples according to photometrical and dynamical properties such as colour, local environment and infall time. The completeness of the catalogue and our large sample allow us to analyse the velocity dispersion and the luminosity functions of the identified populations. We found evidence of a cluster still in its collapsing phase. The LF of the red population of A2151 shows a deficit of dwarf red galaxies. Moreover, the normalized LFs of the red and blue populations of A2151 are comparable to the red and blue LFs of the field, even if the blue galaxies start dominating one magnitude fainter and the red LF is well represented by a single Schechter function rather than a double Schechter function. We discuss how the evolution of cluster galaxies depends on their mass: bright and intermediate galaxies are mainly affected by dynamical friction and internal/mass quenching, while the evolution of dwarfs is driven by environmental processes which need time and a hostile cluster environment to remove the gas reservoirs and halt the star formation.