HALO MASS DEPENDENCE OF H I AND O VI ABSORPTION: EVIDENCE FOR DIFFERENTIAL KINEMATICS

We studied a sample of 14 galaxies (0.1 < z < 0.7) using HST/WFPC2 imaging and high-resolution HST/COS or HST/STIS quasar spectroscopy of Ly alpha, Ly beta, and O VI lambda lambda 1031, 1037 absorption. The galaxies, having 10.8 <= log(M-h/M-circle dot) <= 12.2, lie within D = 300 kpc of quasar sightlines, probing out to D/R-vir = 3. When the full range of M-h and D/R-vir of the sample are examined, similar to 40% of the H I absorbing clouds can be inferred to be escaping their host halo. The fraction of bound clouds decreases as D/R-vir increases such that the escaping fraction is similar to 15% for D/R-vir < 1, similar to 45% for 1 <= D/R-vir < 2, and similar to 90% for 2 <= D/R-vir < 3. Adopting the median mass logM(h)/M-circle dot = 11.5 to divide the sample into higher and lower mass galaxies, we find a mass dependency for the hot circumgalactic medium kinematics. To our survey limits, O VI absorption is found in only similar to 40% of the H I clouds in and around lower mass halos as compared to similar to 85% around higher mass halos. For D/R-vir < 1, lower mass halos have an escape fraction of similar to 65%, whereas higher mass halos have an escape fraction of similar to 5%. For 1 <= D/R-vir < 2, the escape fractions are similar to 55% and similar to 35% for lower mass and higher mass halos, respectively. For 2 <= D/R-vir < 3, the escape fraction for lower mass halos is similar to 90%. We show that it is highly likely that the absorbing clouds reside within 4R(vir) of their host galaxies and that the kinematics are dominated by outflows. Our finding of differential kinematics is consistent with the scenario of differential wind recycling proposed by Oppenheimer et al. We discuss the implications for galaxy evolution, the stellar to halo mass function, and the mass-metallicity relationship of galaxies.