Bright Lyman-alpha Emitters at z~9: constraints on the luminosity
  function from HiZELS
  New results are presented, as part of the Hi-z Emission Line Survey (HiZELS),
from the largest area survey to date (1.4 sq.deg) for Lyman-alpha emitters
(LAEs) at z~9. The survey, which is primarily targeting 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 and reaches 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. Only 2 candidates were found out of 1517 line emitters and those
were rejected as LAEs after follow-up observations. The limit on the space
density of bright LAEs is improved by 3 orders of magnitude, 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 LAEs. The potential
contamination of future 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.
