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Keck/MOSFIRE Spectroscopy of z = 7–8 Galaxies: Lyα Emission from a Galaxy at z = 7.66

Song, Mimi and Finkelstein, Steven L. and Livermore, Rachael C. and Capak, Peter L. and Dickinson, Mark and Fontana, Adriano (2016) Keck/MOSFIRE Spectroscopy of z = 7–8 Galaxies: Lyα Emission from a Galaxy at z = 7.66. Astrophysical Journal, 826 (2). Art. No. 113. ISSN 0004-637X.

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We report the results from some of the deepest Keck/Multi-Object Spectrometer For Infra-Red Exploration data yet obtained for candidate z gsim 7 galaxies. Our data show one significant line detection with 6.5σ significance in our combined 10 hr of integration which is independently detected on more than one night, thus ruling out the possibility that the detection is spurious. The asymmetric line profile and non-detection in the optical bands strongly imply that the detected line is Lyα emission from a galaxy at z(Lyα) = 7.6637 ± 0.0011, making it the fourth spectroscopically confirmed galaxy via Lyα at z > 7.5. This galaxy is bright in the rest-frame ultraviolet (UV; M_(UV) ~ −21.2) with a moderately blue UV slope β=-2.2_(-0.2)^(+0.3), and exhibits a rest-frame Lyα equivalent width of EW(Lyα) ~ 15.6_(-3.6)^(+5.9) Å. The non-detection of the 11 other z ~ 7–8 galaxies in our long 10 hr integration, reaching a median 5σ sensitivity of 28 Å in the rest-frame EW(Lyα), implies a 1.3σ deviation from the null hypothesis of a non-evolving distribution in the rest-frame EW(Lyα) between 3 < z < 6 and z = 7–8. Our results are consistent with previous studies finding a decline in Lyα emission at z > 6.5, which may signal the evolving neutral fraction in the intergalactic medium at the end of the reionization epoch, although our weak evidence suggests the need for a larger statistical sample to allow for a more robust conclusion.

Item Type:Article
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URLURL TypeDescription
Finkelstein, Steven L.0000-0001-8519-1130
Capak, Peter L.0000-0003-3578-6843
Dickinson, Mark0000-0001-5414-5131
Additional Information:© 2016 The American Astronomical Society. Received 2016 February 5; revised 2016 April 23; accepted 2016 May 1; published 2016 July 26. We would like to thank the anonymous referee for valuable suggestions which improved this paper, and N. Scoville, L. Murchikova, S. Manohar, and B. Darvish for their work during observing runs. M.S. acknowledges support from the NSF AAG award AST-1518183. M.S. and S.L.F. acknowledge support from the NASA Astrophysics and Data Analysis Program award #NNX15AM02G issued by JPL/Caltech, as well as a NASA Keck PI Data Award, administered by the NASA Exoplanet Science Institute. This research is based on observations made with the Keck Telescope. The Observatory was made possible by the financial support of the W.M. Keck Foundation. We recognize and acknowledge the cultural role and reverence that the summit of Mauna Kea has within the indigenous Hawaiian community. Facilities: Keck:I (MOSFIRE) - KECK I Telescope, HST (ACS - Hubble Space Telescope satellite, WFC3) - , VLT (HAWK-I) - .
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
W. M. Keck FoundationUNSPECIFIED
Subject Keywords:galaxies: evolution; galaxies: formation; galaxies: high-redshift
Issue or Number:2
Record Number:CaltechAUTHORS:20160802-071441496
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Official Citation:Mimi Song et al 2016 ApJ 826 113
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:69371
Deposited By: Ruth Sustaita
Deposited On:02 Aug 2016 23:42
Last Modified:09 Mar 2020 13:18

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