MAGIICAT II. General characteristics of the MgII absorbing circumgalactic medium

Abstract

We examine the Mg II absorbing circumgalactic medium (CGM) for the 182 intermediate redshift (0.072 ≤ z ≤ 1.120) galaxies in the "Mg II Absorber-Galaxy Catalog" (MAGIICAT). We parameterize the anti-correlation between equivalent width, Wr (2796), and impact parameter, D, with a log-linear fit, and show that a power law poorly describes the data. We find that higher luminosity galaxies have larger Wr (2796) at larger D (4.3σ). The covering fractions, fc , decrease with increasing D and Wr (2796) detection threshold. Higher luminosity galaxies have larger fc ; no absorption is detected in lower luminosity galaxies beyond 100 kpc. Bluer and redder galaxies have similar fc for D < 100 kpc, but for D > 100 kpc, bluer galaxies have larger fc , as do higher redshift galaxies. The "absorption radius," R(L) = R *(L/L*)β, which we examine for four different W r (2796) detection thresholds, is more luminosity sensitive to the B-band than the K-band, more sensitive for redder galaxies than for bluer galaxies, and does not evolve with redshift for the K-band, but becomes more luminosity sensitive toward lower redshift for the B-band. These trends clearly indicate a more extended Mg II absorbing CGM around higher luminosity, bluer, and higher redshift galaxies. Several of our findings are in conflict with other works. We address these conflicts and discuss the implications of our results for the low-ionization, intermediate redshift CGM. © 2013. The American Astronomical Society. All rights reserved.