Schmidt, K. B.K. B.SchmidtTreu, T.T.TreuBradač, M.M.BradačVulcani, BenedettaBenedettaVulcaniHuang, K. -H.K. -H.HuangHoag, A.A.HoagMaseda, M.M.MasedaGuaita, L.L.GuaitaPENTERICCI, LauraLauraPENTERICCIBrammer, G. B.G. B.BrammerDijkstra, M.M.DijkstraDressler, A.A.DresslerFONTANA, AdrianoAdrianoFONTANAHenry, A. L.A. L.HenryJones, T. A.T. A.JonesMason, C.C.MasonTrenti, M.M.TrentiWang, X.X.Wang2020-05-082020-05-0820160004-637Xhttp://hdl.handle.net/20.500.12386/24650We present a census of Lyα emission at z≳ 7, utilizing deep near-infrared Hubble Space Telescope grism spectroscopy from the first six completed clusters of the Grism Lens-Amplified Survey from Space (GLASS). In 24/159 photometrically selected galaxies we detect emission lines consistent with Lyα in the GLASS spectra. Based on the distribution of signal-to-noise ratios and on simulations, we expect the completeness and the purity of the sample to be 40%-100% and 60%-90%, respectively. For the objects without detected emission lines we show that the observed (not corrected for lensing magnification) 1σ flux limits reach 5 × 10<SUP>-18</SUP> erg s<SUP>-1</SUP> cm<SUP>-2</SUP> per position angle over the full wavelength range of GLASS (0.8-1.7 μm). Based on the conditional probability of Lyα emission measured from the ground at z∼ 7, we would have expected 12-18 Lyα emitters. This is consistent with the number of detections, within the uncertainties, confirming the drop in Lyα emission with respect to z∼ 6. Deeper follow-up spectroscopy, here exemplified by Keck spectroscopy, is necessary to improve our estimates of completeness and purity and to confirm individual candidates as true Lyα emitters. These candidates include a promising source at z = 8.1. The spatial extent of Lyα in a deep stack of the most convincing Lyα emitters with < z> = 7.2 is consistent with that of the rest-frame UV continuum. Extended Lyα emission, if present, has a surface brightness below our detection limit, consistent with the properties of lower-redshift comparison samples. From the stack we estimate upper limits on rest-frame UV emission line ratios and find {f}<SUB>{{C</SUB>}{{IV}}}/{f}<SUB>{Ly</SUB>α }≲ 0.32 and {f}<SUB>{{C</SUB>}{{III}}]}/{f}<SUB>{Ly</SUB>α }≲ 0.23, in good agreement with other values published in the literature.STAMPAenArticle10.3847/0004-637X/818/1/382-s2.0-84959095960000370370800038https://iopscience.iop.org/article/10.3847/0004-637X/818/1/382016ApJ...818...38SFIS/05 - ASTRONOMIA E ASTROFISICA