Deep spectroscopy in nearby galaxy clusters - V. The Perseus cluster

Dwarfs are the largest population of galaxies in number in the nearby Universe. Deep spectroscopic data are still missing to obtain a better understanding of their formation and evolution processes. This study shows the results obtained from a spectroscopic campaign in the Perseus cluster. We have obtained 963 new galaxy spectra. We have measured the recessional velocity of the galaxies by using a cross-correlation technique. These data have been used to obtain the cluster membership, the dynamics of the galaxies, and the spectroscopic luminosity function (LF) of the cluster. The cluster membership was obtained by using the peak + gap technique, reporting a total of 403 galaxies as cluster members within 1.4r200. The mean velocity and velocity dispersion of the cluster galaxies are Vc = 5258 km s−1 and σc = 1040 km s−1, respectively. We obtained M200 = 1.2 × 1015 M⊙ and r200 = 2.2 Mpc for this cluster. The clusters members were classified blue and red according to their g − r stellar colour. The velocity dispersion of these two families of galaxies is different, indicating that the blue galaxies can be classified as recently accreted into the cluster. We present the spectroscopic galaxy LF of the cluster. This function turned to be flat: α = 0.99 ± 0.06. In addition, blue and red galaxies show similar densities in the faint end of the LF. This indicates that Perseus does not have a population of red dwarf galaxias as large as other nearby clusters. We have compared the LF of the Perseus cluster with other spectroscopic LFs of nearby clusters and those from cosmological simulations. This comparison shows that the spectroscopic LF of nearby galaxy cluster is far from universal.