  Recent observations have indicated the existence of dust in high-redshift
galaxies, however, the dust properties in them are still unknown. Here we
present theoretical constraints on dust properties in Lyman break galaxies
(LBGs) at z=3 by post-processing a cosmological smoothed particle hydrodynamics
simulation with radiative transfer calculations. We calculate the dust
extinction in 2800 dark matter halos using the metallicity information of
individual gas particles in our simulation. We use only bright galaxies with
rest-frame UV magnitude M_1700 < -20 mag, and study the dust size,
dust-to-metal mass ratio, and dust composition. From the comparison of
calculated color excess between B and V-band (i.e., E(B-V)) and the
observations, we constrain the typical dust size, and show that the
best-fitting dust grain size is ~ 0.05 micron, which is consistent with the
results of theoretical dust models for Type-II supernova. Our simulation with
the dust extinction effect can naturally reproduce the observed rest-frame UV
luminosity function of LBGs at z=3 without assuming an ad hoc constant
extinction value. In addition, in order to reproduce the observed mean E(B-V),
we find that the dust-to-metal mass ratio needs to be similar to that of the
local galaxies, and that the graphite dust is dominant or at least occupy half
of dust mass.
