  We present a self-consistent, semi-analytical LCDM model of star formation
and reionization. For the cosmological parameters favored by the WMAP data, our
models consistently reproduce the optical depth to reionization, redshift of
reionization and the observed luminosity functions (LF) and hence the star
formation rate (SFR) density at 3<z<6 for a reasonable range of model
parameters. While simple photoionization feedback produces the correct shape of
LF at z = 6, for $z = 3$ we need additional feedback that suppresses star
formation in halos with 10<log(M/M_\odot)<11. Models with prolonged continuous
star formation activities are preferred over those with short bursts as they
are consistent with the existence of a Balmer break in considerable fraction of
observed galaxies even at z~6. The halo number density evolution from the
standard LCDM structure formation model that fits LF up to z=6 is consistent
with the upper limits on z~7 LF and source counts at 8<z<12 obtained from the
HUDF observations without requiring any dramatic change in the nature of star
formation. However, to reproduce the observed LF at 6<z<10, obtained from the
near-IR observations around strong lensing clusters, we need a strong evolution
in the IMF, reddening correction and the mode of star formation at z>8.
Molecular cooled halos, which may be important for reionizing the universe, are
not detectable in the present deep field observations. However, their presence
and contribution to reionization can be inferred indirectly from the redshift
evolution of the LF at 6<z< 12.Accurately measuring the LF at high z can be
used to understand the nature of star formation in the dark ages and probe the
history of reionization. (Abridged)
