MAGIICAT I. THE Mg II ABSORBER-GALAXY CATALOG

We describe the Mg II Absorber-Galaxy Catalog, MAGIICAT, a compilation of 182 spectroscopically identified intermediate redshift (0.07 ≤ z ≤ 1.1) galaxies with measurements of Mg II λλ2796, 2803 absorption from their circumgalactic medium within projected distances of 200 kpc from background quasars. In this work, we present isolated galaxies, which are defined as having no spectroscopically identified galaxy within a projected distance of 100 kpc and a line of sight velocity separation of 500 km s–1. We standardized all galaxy properties to the ΛCDM cosmology and galaxy luminosities, absolute magnitudes, and rest-frame colors to the B- and K-band on the AB system. We present galaxy properties and rest-frame Mg II equivalent width, Wr (2796), versus galaxy redshift. The well-known anti-correlation between Wr (2796) and quasar-galaxy impact parameter, D, is significant to the 8σ level. The mean color of MAGIICAT galaxies is consistent with an Sbc galaxy for all redshifts. We also present B- and K-band luminosity functions for different Wr (2796) and redshift subsamples: weak absorbing [Wr (2796) < 0.3 A], strong absorbing [Wr (2796) ≥ 0.3 A], low redshift (z < z), and high redshift (z ≥ z), where z = 0.359 is the median galaxy redshift. Rest-frame color B – K correlates with MK at the 8σ level for the whole sample but is driven by the strong absorbing, high-redshift subsample (6σ). Using MK as a proxy for stellar mass and examining the luminosity functions, we infer that in lower stellar mass galaxies, Mg II absorption is preferentially detected in blue galaxies and the absorption is more likely to be weak.