2017ApJ...846L..24M

O vi absorption in quasar spectra caused by intervening circumgalactic atmospheres suggests a downturn in the atmospheric column density in sightlines passing beyond about 100 kpc from central star-forming galaxies. This turnover supports the hypothesis that the oxygen originates in the central galaxies. When converted into oxygen space density using an Abel integral inversion, the O vi columns require 10⁹M_☉ of oxygen concentrated near 100 kpc. Circumgalactic gas within this radius cools in less than 1 Gyr and radiates ∼10^42.2 erg s^–1 overall. The feedback power necessary to maintain such oxygen-rich atmospheres for many Gyr cannot be easily supplied by galactic supernovae. However, massive central black holes in star-forming galaxies may generate sufficient accretion power and intermittent shock waves at r∼100 kpc to balance circumgalactic radiation losses in late-type L^*^ galaxies. The relative absence of O vi absorption observed in early-type, passive L^*^ galaxies may arise from enhanced AGN feedback from their more massive central black holes.