We examine the effects of SMBH feedback on the CGM using a cosmological hydrodynamic simulation \citep[{ \sc Romulus25};][]{ Tremmel2017} and a set of four zoom-in `genetically modified' Milky Way-mass galaxies sampling different evolutionary paths. By tracing the distribution of metals in the circumgalactic medium (CGM), we show that \ion{ O}{ 6} is a sensitive indicator of supermassive black hole (SMBH) feedback. First, we calculate the column densities of \ion{ O}{ 6} in simulated Milky Way-mass galaxies and compare them with observations from the COS-Halos Survey. Our simulations show column densities of \ion{ O}{ 6} in the CGM consistent with those of COS-Halos star forming and quenched galaxies. These results contrast with those from previous simulation studies which typically underproduce CGM column densities of \ion{ O}{ 6}. We determine that a galaxy's star formation history and assembly record have little effect on the amount of \ion{ O}{ 6} in its CGM. Instead, column densities of \ion{ O}{ 6} are closely tied to galaxy halo mass and BH growth history. The set of zoom-in, genetically modified Milky Way-mass galaxies indicates that the SMBH drives highly metal-enriched material out into its host galaxy's halo which in turn elevates the column densities of \ion{ O}{ 6} in the CGM.
Categories: astro-ph.GA