The relation between galaxies and the warm-hot circumgalactic medium...
By Nastasha Wijers
The hot gas around galaxies holds the key to improving our understanding of the fueling and feedback processes that regulate their growth. Detecting the emission of this dilute phase is highly challenging and biased to higher-density clumps, making absorption studies an attractive alternative. We have described soft X-ray line absorption around galaxies in the EAGLE cosmological, hydrodynamical simulations at redshift 0.1. We find that column densities of O VII and O VIII are high enough to produce absorption lines that should be detectable with the Athena X-IFU in background quasar spectra. This detectable absorption exists around Milky-Way-mass galaxies (especially O VII) as well as more massive galaxies, and out to close to the halo virial radius. The absorption by these ions traces the volume-filling, hot gas phase that has been difficult to detect and constrain in extragalactic, Milky-Way-mass haloes.