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Keck Spectroscopy of Faint 3 > z > 7 Lyman Break Galaxies: A High Fraction of Line Emitters at Redshift Six

Stark, Daniel P. and Ellis, Richard S. and Ouchi, Masami (2011) Keck Spectroscopy of Faint 3 > z > 7 Lyman Break Galaxies: A High Fraction of Line Emitters at Redshift Six. Astrophysical Journal Letters, 728 (1). Art. No. L2. ISSN 2041-8205.

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As Lyα photons are scattered by neutral hydrogen, a change with redshift in the Lyα equivalent width (EW) distribution of distant galaxies offers a promising probe of the degree of ionization in the intergalactic medium and hence when cosmic reionization ended. This simple test is complicated by the fact that Lyα emission can also be affected by variations in the kinematics and dust content of the host galaxies. In the first paper in this series, we demonstrated both a luminosity- and redshift-dependent trend in the fraction of Lyα emitters seen within color-selected "Lyman break" galaxies (LBGs) over the range 3 < z < 6; lower luminosity galaxies and those at higher redshift show an increased likelihood of strong emission. Here, we present the results from 12.5 hr exposures with the Keck DEIMOS spectrograph focused primarily on LBGs at z ≃ 6 which enable us to confirm the redshift dependence of line emission more robustly and to higher redshift than was hitherto possible. We find that 54% ± 11% of faint z ≃ 6 LBGs show strong (W_(Lyα,0) >25 Å) emission, an increase of 55% from a sample of similarly luminous z ≃ 4 galaxies. With a total sample of 74 z ≃ 6 LBGs, we determine the luminosity-dependent Lyα EW distribution. Assuming continuity in these trends to the new population of z ≃ 7 sources located with the Hubble WFC3/IR camera, we predict that unless the neutral fraction rises in the intervening 200 Myr, the success rate for spectroscopic confirmation using Lyα emission should be high.

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Ellis, Richard S.0000-0001-7782-7071
Additional Information:© 2011 American Astronomical Society. Received 2010 September 26; accepted 2010 December 6; published 2011 January 18. We thank the referee for valuable comments which improved the manuscript. D.P.S. acknowledges financial support from a postdoctoral fellowship from the Science Technology and Research Council and a Schlumberger Interdisciplinary Research Fellowship at Darwin College, University of Cambridge. M.O. is grateful to financial support from Carnegie Observatories via the Carnegie fellowship.
Funding AgencyGrant Number
Science Technology and Research CouncilUNSPECIFIED
University of Cambridge Darwin CollegeUNSPECIFIED
Carnegie Observatories Carnegie fellowshipUNSPECIFIED
Subject Keywords:galaxies: evolution – galaxies: formation – galaxies: high-redshift – galaxies: starburst
Issue or Number:1
Classification Code:PACS: 98.54.Ep; 98.62.Py; 98.62.Ai; 98.62.Ra; 98.62.Qz; 95.85.Kr
Record Number:CaltechAUTHORS:20110228-113052568
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Official Citation:Daniel P. Stark et al. 2011 ApJ 728 L2 doi: 10.1088/2041-8205/728/1/L2
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:22549
Deposited By: Benjamin Perez
Deposited On:28 Feb 2011 22:02
Last Modified:26 Nov 2019 11:15

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