A Photometric and Spectroscopic Study of Dwarf and Giant Galaxies in the Coma Cluster. II. Spectroscopic Observations

This is the second paper in a series studying the photometric and spectroscopic properties of galaxies of different luminosities in the Coma Cluster. We present the sample selection, spectroscopic observations, and completeness functions. To study the spectral properties of galaxies as a function of their local environment, two fields were selected for spectroscopic observations to cover both the core (Coma 1) and outskirts (i.e., southwest of the core and centered on NGC 4839; Coma 3) of the cluster. To maximize the efficiency of spectroscopic observations, two subsamples were defined, consisting of "bright" and "faint" galaxies, both drawn from magnitude-limited parent samples. Medium-resolution spectroscopy (6-9 Å) was then carried out for a total of 490 galaxies in both fields (302 in Coma 1 and 188 in Coma 3), using the WYFFOS multifiber spectrograph on the William Herschel Telescope. The galaxies cover a range of 12 < R < 20, corresponding to -23 < MR < -15 (H0 = 65 km s-1 Mpc-1). The redshifts for these galaxies are measured with an accuracy of 75 km s-1. The spectral line strengths and equivalent widths are also measured for the same galaxies and analyzed in the next paper of this series. A total of 189 (Coma 1) and 90 (Coma 3) galaxies are identified as members of the Coma Cluster. An analysis of the colors show that only two members of the Coma Cluster in our sample have B - R > 2. The completeness functions for our sample are calculated. These show that the bright sample is 65% complete at R < 17 mag, becoming increasingly incomplete toward fainter magnitudes, while the faint sample follows a monotonically decreasing completeness function at R > 19 mag.