MAGiiCAT IV. KINEMATICS OF THE CIRCUMGALACTIC MEDIUM AND EVIDENCE FOR QUIESCENT EVOLUTION AROUND RED GALAXIES

Abstract

ABSTRACT The equivalent widths of Mg II ?> absorption in the circumgalactic medium (CGM) trace the global star formation rate up to z < 6, are larger for star-forming galaxies than passively evolving galaxies, and decrease with increasing distance from the galaxy. We delve further into the physics involved by investigating gas kinematics and cloud column density distributions as a function of galaxy color, redshift, and projected distance from the galaxy (normalized by galaxy virial radius, D/R vir). For 39 isolated galaxies at 0.3 < z gal < 1.0, we have detected Mg II ?> absorption in high-resolution (Δv ≃ 6.6 km s−1) spectra of background quasars within a projected distance of 7 < D < 190 kpc. We characterize the absorption velocity spread using pixel-velocity two-point correlation functions. Velocity dispersions and cloud column densities for blue galaxies do not differ with redshift nor with D/R vir. This suggests that outflows continually replenish the CGM of blue galaxies with high velocity dispersion, large column density gas out to large distances. Conversely, absorption hosted by red galaxies evolves with redshift where the velocity dispersions (column densities) are smaller (larger) at z gal < 0.656. After taking into account larger possible velocities in more massive galaxies, we find that there is no difference in the velocity dispersions or column densities for absorption hosted by red galaxies with D/R vir. Thus, a lack of outflows in red galaxies causes the CGM to become more quiescent over time, with lower velocity dispersions and larger column densities toward lower z gal. The quenching of star formation appears to affect the CGM out to D/R vir = 0.75.