Title: GTC Observations of an Overdense Region of LAEs at z=6.5,
Abstract: We present the results of our search for the faint galaxies near the end of
the Reionisation Epoch. This has been done using very deep OSIRIS images
obtained at the Gran Telescopio Canarias (GTC). Our observations focus around
two close, massive Lyman Alpha Emitters (LAEs) at redshift 6.5, discovered in
the SXDS field within a large-scale overdense region (Ouchi et al. 2010). The
total GTC observing time in three medium band filters (F883w35, F913w25 and
F941w33) is over 34 hours covering $7.0\times8.5$ arcmin$^2$ (or $\sim30,000$
Mpc$^3$ at $z=6.5$). In addition to the two spectroscopically confirmed LAEs in
the field, we have identified 45 other LAE candidates. The preliminary
luminosity function derived from our observations, assuming a spectroscopic
confirmation success rate of $\frac{2}{3}$ as in previous surveys, suggests
this area is about 2 times denser than the general field galaxy population at
$z=6.5$. If confirmed spectroscopically, our results will imply the discovery
of one of the earliest protoclusters in the universe, which will evolve to
resemble the most massive galaxy clusters today.