The HiZELS/UKIRT large area survey for bright Lyman-alpha emitters at
  z~9
  We present the largest area survey to date (1.4 deg2) for Lyman-alpha
emitters (LAEs) at z~9, as part of the Hi-z Emission Line Survey (HiZELS). The
survey, which primarily targets H-alpha emitters at z < 3, uses the Wide Field
CAMera on the United Kingdom Infrared Telescope and a custom narrow-band filter
in the J band to reach a Lyman-alpha luminosity limit of ~10^43.8 erg/s over a
co-moving volume of 1.12x10^6 Mpc^3 at z = 8.96+-0.06. Two candidates were
found out of 1517 line emitters, but those were rejected as LAEs after
follow-up observations. This improves the limit on the space density of bright
Lyman-alpha emitters by 3 orders of magnitude and is consistent with
suppression of the bright end of the Lyman-alpha 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 Lyman-alpha emitters. The
potential contamination of narrow-band Lyman-alpha 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.
