  We perform Monte-Carlo radiative transfer calculations to model the Lyman
alpha properties of galaxies in high-resolution, zoom-in cosmological
simulations at z ~ 6.6. The simulations include both constrained and
unconstrained runs, representing respectively a highly overdense region and an
average field. Different galactic wind models are used in the simulations in
order to investigate the effects of these winds on the apparent Ly alpha
properties of galaxies. We find that, for models including galactic winds, the
Ly alpha properties of massive galaxies residing in the overdense region match
well recent observations of luminous Ly alpha emitters (LAEs) at z ~ 6-7, in
terms of apparent Ly alpha luminosity, Ly alpha line width and Ly alpha
equivalent width distributions. Without winds, the same galaxies appear less Ly
alpha bright as a result of both differences in the line profile emerging from
galaxies themselves, and, in the distributions of neutral gas in the
circumgalactic (CGM) and intergalactic medium (IGM). We also study the
relations between apparent Ly alpha luminosity and various galaxy properties:
stellar mass, star formation rate (SFR) and host halo mass. At fixed halo mass,
the apparent Ly alpha luminosity of galaxies appears to depend on the
large-scale environment while this is no longer true for galaxies at a given
stellar mass or SFR. We provide simple linear fits to these relations that can
be used for quickly constructing mock LAE samples from N-body simulations. Our
results suggest that the observed luminous LAEs at z ~ 6.6 are hosted by
~10^{12} h^{-1} Mo, dark matter haloes, residing in large, overdense ionized
regions.
