Texas Spectroscopic Search for Ly Emission at the End of Reionization. II. The Deepest Near-infrared Spectroscopic Observation at z 7
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AbstractRealizing the utility of Ly emission to trace the evolution of the intergalactic medium (IGM) during the epoch of reionization requires deep spectroscopy across the boundary of optical and near-infrared (NIR) spectrographs at z7.2 when Ly emission is at 1 m. Our Texas Spectroscopic Search for Ly Emission at the End of Reionization includes 18 nights of deep spectroscopic observations using the Keck DEIMOS (optical) and MOSFIRE (NIR) spectrographs. Within this data set we observe Ly emission from 183 photometric-redshift-selected galaxies at z=5.58.3 from the Cosmic Assembly Near infrared Deep Extragalactic Legacy Survey. Our overlapping MOSFIRE observations, over 84 galaxies in total, provide the deepest NIR spectroscopic data yet obtained for Ly from galaxies z>7, with >16 hr integration time for four observed galaxies. Here we analyze these four targets, and we report the discovery of a new z=7.60 Ly detection as well as provide an updated observation of the previously confirmed z=7.51 Ly emission from Finkelstein et al. with a 3longer exposure time. Our analysis of these Ly emission-line profiles reveals a significant asymmetric shape. The detection of Ly from two out of three bright sources (MUV < 20.25) could imply that these bright galaxies inhabit ionized bubbles in a partially neutral IGM, although deeper exposures may reveal Ly emission in the fainter source.
