Journal Article

No evidence for Lyman α emission in spectroscopy of <i>z</i> > 7 candidate galaxies

Joseph Caruana, Andrew J. Bunker, Stephen M. Wilkins, Elizabeth R. Stanway, Mark Lacy, Matt J. Jarvis, Silvio Lorenzoni and Samantha Hickey

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 427, issue 4, pages 3055-3070
Published in print December 2012 | ISSN: 0035-8711
Published online December 2012 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2012.21996.x
No evidence for Lyman α emission in spectroscopy of z > 7 candidate galaxies

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We present Gemini/Gemini Near Infrared Spectrograph (GNIRS) spectroscopic observations of four z-band (z ≈ 7) dropout galaxies and Very Large Telescope (VLT)/XSHOOTER observations of one z-band dropout and three Y-band (z ≈ 8–9) dropout galaxies in the Hubble Ultra Deep Field, which were selected with Wide Field Camera 3 imaging on the Hubble Space Telescope. We find no evidence of Lyman α emission with a typical 5σ sensitivity of 5 × 10−18 erg cm−2 s−1, and use the upper limits on Lyman α flux and the broad-band magnitudes to constrain the rest-frame equivalent widths for this line emission. Accounting for incomplete spectral coverage, we survey 3.0 z-band dropouts and 2.9 Y-band dropouts to a Lyman α rest-frame equivalent width limit >120 Å (for an unresolved emission line); for an equivalent width limit of 50 Å the effective numbers of drop-outs surveyed fall to 1.2 z-band drop-outs and 1.5 Y-band drop-outs. A simple model where the fraction of high rest-frame equivalent width emitters follows the trend seen at z = 3–6.5 is inconsistent with our non-detections at z = 7–9 at the ≈1σ level for spectrally unresolved lines, which may indicate that a significant neutral H i fraction in the intergalactic medium suppresses the Lyman α line in z-drop and Y-drop galaxies at z > 7.

Keywords: galaxies: evolution; galaxies: formation; galaxies: high-redshift; galaxies: starburst; ultraviolet: galaxies

Journal Article.  9067 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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