Effects of dust grains on early galaxy evolution
  Stars form out of molecular gas and supply dust grains during their last evolutionary stages; in turn hydrogen molecules (H2) are produced more efficiently on dust grains. Therefore, dust can drastically accelerate H2 formation, leading to an enhancement of star formation activity. In order to examine the first formation of stars and dust in galaxies, we model the evolution of galaxies in the redshift range of 5<z<20. In particular, we focus on the interplay between dust formation in Type II supernova ejecta and H2 production on dust grains. Such effect causes an enhancement of star formation rate by an order of magnitude on a timescale (~3--5 galactic dynamical times) shorter than the Hubble timescale. We also find that about half of the radiative energy from stars is reprocessed by dust grains and is finally radiated in the far infrared (FIR). Typical star formation rates and luminosities (FIR, UV and metal-line luminosities) are calculated for a large set of (M_vir, z_vir). Using these results and the Press-Schechter formalism, we calculate galaxy number counts and integrated light from high-redshift (z>5) galaxies in sub-millimetre and near-infrared bands. We find that: i) ALMA can detect dust emission from several thousands of galaxies per square degree, and ii) NGST can detect the stellar emission from 10^6 galaxies per square degree. Further observational checks of our predictions include the integrated flux of metal (oxygen and carbon) lines. We finally discuss possible color selection strategies for high-redshift galaxy searches. 
H. Hirashita, A. Ferrara (Osservatorio Astrofisico di Arcetri)