The 50 Mpc Galaxy Catalog (50 MGC): Consistent and Homogeneous Masses, Distances, Colors, and Morphologies

We assemble a catalog of 15424 nearby galaxies within 50 Mpc with consistent and homogenized mass, distance, and morphological type measurements. Our catalog combines galaxies from HyperLeda, the NASA-Sloan Atlas, and the Catalog of Local Volume Galaxies. Distances for the galaxies combine best-estimates for flow-corrected redshift-based distances with redshift-independent distances. We also compile magnitude and color information for 11740 galaxies. We use the galaxy colors to estimate masses by creating self-consistent color-mass-to-light ratio relations in four bands; we also provide color transformations of all colors into Sloan g-i by using galaxies with overlapping color information. We compile morphology information for 13744 galaxies, and use the galaxy color information to separate early- and late-type galaxies. This catalog is widely applicable for studies of nearby galaxies and for placing these studies in the context of more distant galaxies. We present one application here: a preliminary analysis of the nuclear X-ray activity of galaxies. Out of 1506 galaxies within the sample that have available Chandra X-ray observations, we find that 291 have detected nuclear sources. Of the 291 existing Chandra detections, 249 have log(L-X) > 38.3 and available stellar mass estimates. We find that the X-ray active fractions in early-type galaxies are higher than in late-type galaxies, especially for galaxy stellar masses between 10(9) and 10(10.5)M(circle dot). We show that these differences may be due at least in part to the increased astrometric uncertainties in late-type galaxies relative to early types.