The Luminosity Function of Nearby Galaxy Clusters. II. Redshifts and Luminosity Function for Galaxies in the Region of the Centaurus Cluster

We acquired spectra for a random sample of galaxies within a 0.83 squaredegree region centered on the core of the Centaurus cluster. Radial velocitieswere obtained for 225 galaxies to limiting magnitudes of V < 19.5. Of thegalaxies for which velocities were obtained, we find 35% to be member galaxies.Of the 78 member galaxies, magnitudes range from 11.8 < V < 18.5 (-21.6 < M_{V}< -14.9 for H_o = 70 km s^-1 Mpc^-1) with a limiting central surface brightnessof \mu_o < 22.5 mag arcsec^-2. We constructed the cluster galaxy luminosityfunction by using these spectroscopic results to calculate the expectedfraction of cluster members in each magnitude bin. The faint-end slope of theluminosity function using this method is shallower than the one obtained usinga statistical method to correct for background galaxy contamination. We alsouse the spectroscopy results to define surface brightness criteria to establishmembership for the full sample. Using these criteria, we find a luminosityfunction very similar to the one constructed with the statistical backgroundcorrection. For both, we find a faint-end slope alpha ~ -1.4. Adjusting thesurface brightness membership criteria we find that the data are consistentwith a faint-end slope as shallow as -1.22 or as steep as -1.50. We describe inthis paper some of the limitations of using these methods for constructing thegalaxy luminosity function.Comment: 16 pages, 12 figures, accepted by A