R. Martín-Doménech, V. M. Rivilla, I. Jiménez-Serra, D. Quénard, L. Testi, J. Martín-Pintado. 2017. Gran Telescopio Canarias observations of an overdense region of Lyman alpha emitters at z=6.5. Monthly Notices of the Royal Astronomical Society 469, 3, 2646-2661, DOI: 10.1093/mnras/stx782
We present the results of our search near the end of the Reionization Epoch for faint galaxies. 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. The total GTC observing time in three medium band filters (F883w35, F913w25 and F941w33) is over 34 h covering 7.0 x 8.5 arcmin(2) (or similar to 30 000 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 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.