The Self-similarity of the Circumgalactic Medium with Galaxy Virial Mass: Implications for Cold-mode Accretion

We apply halo abundance matching to obtain galaxy virial masses, M _h, and radii, R _vir, 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, W_r (2796), and covering fraction, f_c , as a function of D, D/R _vir, and M _h. Bifurcating the sample at the median mass log M _h/M _⊙ = 12, we find (1) systematic segregation of M _h on the W_r (2796)-D plane (4.0σ) high-mass halos are found at higher D with larger W_r (2796) compared to low-mass halos. On the W_r (2796)-D/R _vir plane, mass segregation vanishes and we find W_r (2796)vprop(D/R _vir)^-2 (8.9σ). (2) High-mass halos have larger f_c at a given D, whereas f_c is independent of M _h at all D/R _vir. (3) f_c is constant with M _h over the range 10.7 <= log M _h/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 M _h/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.