Gas around galaxy haloes - III: hydrogen absorption signatures around
  galaxies and QSOs in the Sherwood simulation suite
  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.
