Michele Trenti (Colorado), Massimo Stiavelli (STScI), Larry Bradley
(STScI), John MacKenty (STScI), Tommaso Treu (UCSB)

Our knowledge of galaxy formation at redshift z>7 has been greatly
improved by the new near-IR capabilities of the Hubble Space
Telescope. We will present the latest determination of the galaxy
luminosity function during the dark ages combining deep WFC3 data to
constrain the evolution of the faint end with a large area parallel
survey (GO 11700; PI Trenti) designed to quantify the abundance of
bright z>7 galaxies and thus evolution in L_*. The observed luminosity
function will be compared to predictions from cosmological simulations
of structure formation to assess the contribution of galaxies to the
reionization of the Universe.  Metal free star formation: contribution
to the re-ionization of the Universe and prospects for detecting
Population III supernovae.