MAGIICAT II. General Characteristics of the MgII Absorbing Circumgalactic Medium

TL;DR

This study analyzes the properties of MgII absorbing circumgalactic medium around 182 intermediate redshift galaxies, revealing correlations with galaxy luminosity, color, and redshift, and highlighting the CGM's dependence on these factors.

Contribution

It provides a comprehensive characterization of the MgII absorbing CGM at intermediate redshifts, including its dependence on galaxy luminosity, color, and redshift, and compares findings with previous studies.

Findings

Higher luminosity galaxies have larger MgII absorption at greater impact parameters.

The covering fraction decreases with impact parameter and detection threshold.

The absorption radius is more sensitive to luminosity in the B-band than in the K-band.

Abstract

We examine the MgII absorbing circumgalactic medium (CGM) for the 182 intermediate redshift (0.072 < z < 1.120) galaxies in the "MgII Absorber-Galaxy Catalog" (MAGIICAT, Nielsen et al.). 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 (4.3 sigma). The covering fractions, f_c, decrease with increasing D and Wr(2796) detection threshold. Higher luminosity galaxies have larger f_c; no absorption is detected in lower luminosity galaxies beyond 100 kpc. Bluer and redder galaxies have similar f_c for D < 100 kpc, but for D > 100 kpc, bluer galaxies have larger f_c, as do higher redshift galaxies. The "absorption radius", R(L)=R*(L/L*)^{beta}$, which we examine for four different Wr(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 towards lower redshift for the B-band. These trends clearly indicate a more extended MgII 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.