Circumgalactic Oxygen Absorption and Feedback

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 ≳ {10}⁹ M _⊙ 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}^\star galaxies. The relative absence of O VI absorption observed in early-type, passive {L}^\star galaxies may arise from enhanced AGN feedback from their more massive central black holes.