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 10⁹ and 10^10.5 M _⊙. 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.