THE CHANGING Ly alpha OPTICAL DEPTH IN THE RANGE 6 < z < 9 FROM THE MOSFIRE SPECTROSCOPY OF Y-DROPOUTS
Tommaso Treu, Kasper B Schmidt, Michele Trenti, Larry D Bradley, Massimo Stiavelli
The Astrophysical Journal Letters | IOP PUBLISHING LTD | Published : 2013
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..View full abstract
Some of the data presented herein were obtained at the W. M. Keck Observatory. The authors recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are grateful to the MOSFIRE team and the staff at Keck for making these observations possible, and to N. P. Konidaris for writing the data reduction pipeline. This Letter is also based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute. We acknowledge support through grants HST-11700, 12572, and 12905, and we thank the referee for a constructive report, which improved the manuscript. T.T. thanks L. Pentericci, E. Vanzella, M. Giavalisco, and D. Stark for useful conversations.