The circumgalactic medium of high redshift galaxies
  We study the properties of the circumgalactic medium (CGM) of high-$z$
galaxies in the metal enrichment simulations presented in Pallottini et al.
2014. At $z=4$, we find that the simulated CGM gas density profiles are
self-similar, once scaled with the virial radius of the parent dark matter
halo. We also find a simple analytical expression relating the neutral hydrogen
equivalent width (${\rm EW}_{\rm HI}$) of CGM absorbers as a function of the
line of sight impact parameter ($b$). We test our predictions against mock
spectra extracted from the simulations, and show that the model reproduces the
${\rm EW}_{\rm HI}(b)$ profile extracted from the synthetic spectra analysis.
When compared with available data, our CGM model nicely predicts the observed
${\rm EW}_{\rm HI}(b)$ in $z\lesssim2$ galaxies, and supports the idea that the
CGM profile does not evolve with redshift.
