The self-similarity of the circumgalactic medium with galaxy virial mass: Implications for cold-mode accretion

Abstract

We apply halo abundance matching to obtain galaxy virial masses, M h, and radii, Rvir, for 183 "isolated" galaxies from the "Mg II Absorber-Galaxy Catalog." All galaxies have spectroscopic redshifts (0.07 ≤ z ≤ 1.12) and their circumgalactic medium (CGM) is probed in Mg II absorption within projected galactocentric distances D ≤ 200 kpc. We examine the behavior of equivalent width, Wr (2796), and covering fraction, fc , as a function of D, D/Rvir, and Mh. Bifurcating the sample at the median mass log M h/M⊙ = 12, we find (1) systematic segregation of Mh on the Wr (2796)-D plane (4.0σ); high-mass halos are found at higher D with larger Wr (2796) compared to low-mass halos. On the Wr (2796)-D/Rvir plane, mass segregation vanishes and we find Wr (2796)∝(D/Rvir)-2 (8.9σ). (2) High-mass halos have larger fc at a given D, whereas fc is independent of Mh at all D/Rvir. (3) fc is constant with Mh over the range 10.7 ≤ log Mh/M⊙ ≤ 13.9 within a given D or D/R vir. The combined results suggest the Mg II absorbing CGM is self-similar with halo mass, even above log Mh/M⊙ ≃ 12, where cold mode accretion is predicted to be quenched. If theory is correct, either outflows or sub-halos must contribute to absorption in high-mass halos such that low- and high-mass halos are observationally indistinguishable using Mg II absorption strength once impact parameter is scaled by halo mass. Alternatively, the data may indicate predictions of a universal shut down of cold-mode accretion in high-mass halos may require revision. © 2013. The American Astronomical Society. All rights reserved.