The HiZELS/UKIRT Large Survey for Bright Lyα Emitters at z ∼ 9
We present the largest area survey to date (1.4 deg2) for Lyα emitters (LAEs) at z ∼ 9, as part of the Hi-z Emission Line Survey (HiZELS). The survey, which primarily targets Hα emitters at z > 3, uses the Wide Field Camera on the United Kingdom Infrared Telescope and a custom narrowband filter in the J band to reach a Lyα luminosity limit of ∼1043.8 erg s−1 over a co-moving volume of 1.12 × 106 Mpc3 at z = 8.96 ± 0.06. Two candidates were found out of 1,517 line emitters, but those were rejected as LAEs after follow-up observations. This improves the limit on the space density of bright Lyα emitters by three orders of magnitude and is consistent with suppression of the bright end of the Lyα luminosity function beyond z ∼ 6. Combined with upper limits from smaller but deeper surveys, this rules out some of the most extreme models for high-redshift Lyα emitters. The potential contamination of narrowband Lyα surveys at z < 7 by Galactic brown dwarf stars is also examined, leading to the conclusion that such contamination may well be significant for searches at 7.7 > z > 8.0, 9.1 > z > 9.5 and 11.7 > z > 12.2.
KeywordsLuminosity Function Dwarf Star Wide Field Camera Narrowband Filter Infrared Telescope
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