Abstract
We conduct a photometric and spectroscopic survey of a 10 deg2 region surrounding the nearby NGC 5846 group of galaxies, using the Canada-France-Hawaii and Keck I telescopes to study the population of dwarf galaxies as faint as MR = -10. Candidates are identified on the basis of quantitative surface brightness and qualitative morphological criteria. Spectroscopic follow up and a spatial correlation analysis provide the basis for affirming group memberships. Altogether, 324 candidates are identified, and 83 have spectroscopic membership confirmation. We argue on statistical grounds that a total of 251 ? 10 galaxies in our sample are group members. The observations, together with archival Sloan Digital Sky Survey, ROSAT, XMM-Newton, and ASCA data, suggest that the giant ellipticals NGC 5846 and NGC 5813 are the dominant components of subgroups separated by 600?kpc in projection and embedded in a 1.6?Mpc diameter dynamically evolved halo. The galaxy population is overwhelmingly early type. The group velocity dispersion is 322?km s-1, its virial mass is 8.4 ? 1013 M?, and M/LR = 320 M? L. The ratio of dwarfs to giants is large compared with other environments in the Local Supercluster studied, and, correspondingly, the luminosity function is relatively steep, with a faint-end Schechter function slope of ?d = -1.3 ? 0.1 (statistical) ?0.1 (systematic) at our completeness limit of MR = -12.
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