The impact of feedback on cosmological gas accretion

Abstract

We investigate how the way galaxies acquire their gas across cosmic time in cosmological hydrodynamic simulations is modified by a comprehensive physical model for baryonic feedback processes. To do so, we compare two simulations - with and without feedback - both evolved with the moving mesh code AREPO. The feedback runs implement the full physics model of the Illustris simulation project, including star formation driven galactic winds and energetic feedback from supermassive black holes. We explore: (a) the accretion rate of material contributing to the net growth of galaxies and originating directly from the intergalactic medium, finding that feedback strongly suppresses the raw, as well as the net, inflow of this 'smoothmode' gas at all redshifts, regardless of the temperature history of newly acquired gas. (b) At the virial radius the temperature and radial flux of inflowing gas is largely unaffected at z = 2. However, the spherical covering fraction of inflowing gas at 0.25 r(vir) decreases substantially, from more than 80 per cent to less than 50 per cent, while the rates of both inflow and outflow increase, indicative of recycling across this boundary.