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The observed high covering fractions of neutral hydrogen (HI) with columndensities above $\sim 10^{17} \rm{cm}^{-2}$ around Lyman-Break Galaxies (LBGs)and bright quasars at redshifts z ~ 2-3 has been identified as a challenge forsimulations of galaxy formation. We use the EAGLE cosmological, hydrodynamicalsimulation, which has been shown to reproduce a wide range of galaxy propertiesand for which the subgrid feedback was calibrated without considering gasproperties, to study the distribution of HI around high-redshift galaxies. Wepredict the covering fractions of strong HI absorbers ($N_{\rm{HI}} \gtrsim10^{17} \rm{cm}^{-2}$) inside haloes to increase rapidly with redshift but todepend only weakly on halo mass. For massive ($M_{200} \gtrsim 10^{12} {\rmM_{\odot}}$) halos the covering fraction profiles are nearly scale-invariantand we provide fitting functions that reproduce the simulation results. Whileefficient feedback is required to increase the HI covering fractions to thehigh observed values, the distribution of strong absorbers in and around halosof a fixed mass is insensitive to factor of two variations in the strength ofthe stellar feedback. In contrast, at fixed stellar mass the predicted HIdistribution is highly sensitive to the feedback efficiency. The fiducial EAGLEsimulation reproduces both the observed global column density distributionfunction of HI and the observed radial covering fraction profiles of strong HIabsorbers around LBGs and bright quasars.

The distribution of neutral hydrogen around high-redshift galaxies and quasars in the EAGLE simulation