Title: Gas around galaxy haloes - III: hydrogen absorption signatures around galaxies and QSOs in the Sherwood simulation suite,
Abstract: Modern theories of galaxy formation predict that galaxies impact on their
gaseous surroundings, playing the fundamental role of regulating the amount of
gas converted into stars. While star-forming galaxies are believed to provide
feedback through galactic winds, Quasi-Stellar Objects (QSOs) are believed
instead to provide feedback through the heat generated by accretion onto a
central supermassive black hole. A quantitative difference in the impact of
feedback on the gaseous environments of star-forming galaxies and QSOs has not
been established through direct observations. Using the Sherwood cosmological
simulations, we demonstrate that measurements of neutral hydrogen in the
vicinity of star-forming galaxies and QSOs during the era of peak galaxy
formation show excess LyA absorption extending up to comoving radii of about
150 kpc for star-forming galaxies and 300 - 700 kpc for QSOs. Simulations
including supernovae-driven winds with the wind velocity scaling like the
escape velocity of the halo account for the absorption around star-forming
galaxies but not QSOs.