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Title: THE CHANGING Lyα OPTICAL DEPTH IN THE RANGE 6 < z < 9 FROM THE MOSFIRE SPECTROSCOPY OF Y-DROPOUTS

We present the MOSFIRE spectroscopy of 13 candidate z ∼ 8 galaxies selected as Y-dropouts as part of the Brightest of Reionization Galaxies pure parallel survey. We detect no significant Lyα emission (our median 1σ rest-frame equivalent width sensitivity is in the range 2-16 Å). Using the Bayesian framework derived in a previous paper, we perform a rigorous analysis of a statistical subsample of non-detections for 10 Y-dropouts, including data from the literature, to study the cosmic evolution of the Lyα emission of Lyman break galaxies. We find that Lyα emission is suppressed at z ∼ 8 by at least a factor of three with respect to z ∼ 6 continuing the downward trend found by previous studies of z-dropouts at z ∼ 7. This finding suggests a dramatic evolution in the conditions of the intergalactic or circumgalactic media in just 300 Myr, consistent with the onset of reionization or changes in the physical conditions of the first generations of star-forming regions.
Authors:
;  [1] ;  [2] ; ;  [3]
  1. Department of Physics, University of California, Santa Barbara, CA 93106-9530 (United States)
  2. Institute of Astronomy and Kavli Institute for Cosmology, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom)
  3. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
Publication Date:
OSTI Identifier:
22215441
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 775; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; DEPTH; DETECTION; EMISSION; EVOLUTION; GALAXIES; RED SHIFT; SENSITIVITY; SPECTROSCOPY; STARS; WIDTH