We present new results from our search for z~7 galaxies from deep spectroscopic observations of candidate z-dropouts in the CANDELS fields. Despite the extremely low flux limits achieved by our sensitive observations, only 2 galaxies have robust redshift identifications, one from its Lyalpha emission line at z=6.65, the other from its Lyman-break, i.e. the continuum discontinuity at the Lyalpha wavelength consistent with a redshift 6.42, but with no emission line. In addition, for 23 galaxies we present deep limits in the Lyalpha EW derived from the non detections in ultra-deep observations. Using this new data as well as previous samples, we assemble a total of 68 candidate z~7 galaxies with deep spectroscopic observations, of which 12 have a line detection. With this much enlarged sample we can place solid constraints on the declining fraction of Lyα emission in z~7 Lyman break galaxies compared to z~6, both for bright and faint galaxies. Applying a simple analytical model, we show that the present data favor a patchy reionization process rather than a smooth one.
@article{arxiv.1403.5466,
title = {New observations of z~7 galaxies: evidence for a patchy reionization},
author = {L. Pentericci and E. Vanzella and A. Fontana and M. Castellano and T. Treu and A. Mesinger and M. Dijkstra and A. Grazian and M. Bradač and C. Conselice and S. Cristiani and J. Dunlop and A. Galametz and M. Giavalisco and E. Giallongo and A. Koekemoer and R. McLure and R. Maiolino and D Paris and D. and P. Santini},
journal= {arXiv preprint arXiv:1403.5466},
year = {2015}
}