A High Space Density of Luminous Lyα Emitters at z ∼ 6.5

Micaela B. Bagley, Claudia Scarlata, Alaina Henry, Marc Rafelski, Matthew Malkan, Harry Teplitz, Y. Sophia Dai, Ivano Baronchelli, James Colbert, Michael Rutkowski, Vihang Mehta, Alan Dressler, Patrick McCarthy, Andrew Bunker, Hakim Atek, Thibault Garel, Crystal L. Martin, Nimish Hathi, Brian Siana

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    24 Scopus citations

    Abstract

    We present the results of a systematic search for Lyα emitters (LAEs) at 6 ≲ z ≲ 7.6 using the HST WFC3 Infrared Spectroscopic Parallel (WISP) Survey. Our total volume over this redshift range is ∼8 × 105 Mpc3, comparable to many of the narrowband surveys despite their larger area coverage. We find two LAEs at z = 6.38 and 6.44 with line luminosities of LLyα ∼ 4.7 × 1043 erg s-1, putting them among the brightest LAEs discovered at these redshifts. Taking advantage of the broad spectral coverage of WISP, we are able to rule out almost all lower-redshift contaminants. The WISP LAEs have a high number density of 7.7 × 10-6 Mpc-3. We argue that the LAEs reside in megaparsec-scale ionized bubbles that allow the Lyα photons to redshift out of resonance before encountering the neutral intergalactic medium. We discuss possible ionizing sources and conclude that the observed LAEs alone are not sufficient to ionize the bubbles.

    Original languageEnglish (US)
    Article number11
    JournalAstrophysical Journal
    Volume837
    Issue number1
    DOIs
    StatePublished - Mar 1 2017

    Bibliographical note

    Funding Information:
    This research was partially supported by a Jet Propulsion Lab/NASA grant to the University of Minnesota (RSA 1541900/NNN12AA01C). Support for HST Programs GO-11696, 12283, 12568, 12902, 13517, 13352, and 14178 was provided by NASA through grants from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.

    Publisher Copyright:
    © 2017. The American Astronomical Society. All rights reserved.

    Keywords

    • cosmology: observations
    • galaxies: high-redshift

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