  We extend a previous study of Lyman Alpha Emitters (LAEs) based on
hydrodynamical cosmological simulations, by including two physical processes
important for LAEs: (a) Lyman Alpha and continuum luminosities produced by
cooling of collisionally excited HI in the galaxy, (b) dust formation and
evolution; we follow these processes on a galaxy-by-galaxy basis. HI cooling on
average contributes 16-18% of the Lyman Alpha radiation produced by stars, but
this value can be much higher in low mass LAEs and further increased if the HI
is clumpy. The continuum luminosity is instead almost completely dominated by
stellar sources. The dust content of galaxies scales with their stellar mass,
M_{dust} is proportional to M_*^0.7 and stellar metallicity, Z_*, such that
M_{dust} is proportional to Z_*^1.7. As a result, the massive galaxies have
Lyman Alpha escape fraction as low as f_alpha=0.1, with a LAE-averaged value
decreasing with redshift such that it is (0.33,0.23) at z =(5.7,6.6). The UV
continuum escape fraction shows the opposite trend with redshift, possibly
resulting from clumpiness evolution. The model successfully reproduces the
observed Lyman Alpha and UV luminosity functions at different redshifts and the
Lyman Alpha equivalent width scatter to a large degree, although the observed
distribution appears to be more more extended than the predicted one. We
discuss possible reasons for such tension.
