2005A&A...434..521S

We present a wide field V-band imaging survey of approximately 1deg² (∼7.2h₇₅^–2Mpc²) in the direction of the nearby cluster of galaxies Abell 2151 (the Hercules Cluster). The data are used to construct the luminosity function (LF) down to M_V≃-14.85, thus allowing us to study the dwarf galaxy population in A2151 for the first time. The obtained global LF is well described by a Schechter function with best-fit parameters α=-1.29^+0.09_–0.08 and M_V^*=-21.41^+0.44_–0.41. The radial dependence of the LF was investigated, with the faint-end slope tending to be slightly steeper in the outermost regions and farther away than the virial radius. Given the presence of significant substructure within the cluster, we also analysed the LFs in three different regions. We find that the dwarf to giant ratio increases from the northern to the southern subcluster, and from low to high local density environments, although these variations are marginally significant (less than 2σ).