Tunable filter imaging of high redshift quasar fields
  We have used the Taurus Tunable Filter to search for Lyman alpha emitters in
the fields of three high redshift quasar fields: two at z~2.2 (MRC B1256-243
and MRC B2158-206) and one at z~4.5 (BR B0019-1522). Our observations had a
field of view of around 35 square arcminutes, and reached AB magnitudes of
magnitudes of ~21 (MRC B1256-243), ~22 (MRC B2158-206), and ~22.6 (BR
B0019-1522), dependent on wavelength. We have identified candidate emission
line galaxies in all three of the fields, with the higher redshift field being
by far the richest. By combining our observations with simulations of the
instrumental response, we estimate the total density of emission line galaxies
in each field. Seventeen candidate emission line galaxies were found in within
1.5 Mpc of BR0019-1522, a number density of 4.9 +/- 1.2 x 10^-3 Mpc^-3,
suggesting a significant galaxy overdensity at z~4.5.
