Abstract:
Systematic surveys are being proposed to discover a significant number of galaxies at z similar or equal to 6, which is now suggested as the epoch at which the reionization era of the universe ends. To plan such surveys, we need a reasonable expectation of the surface density of high-redshift galaxies at different flux limits. Here we present a simple prediction of the surface density of 5.5 less than or equal to z less than or equal to 6.5 galaxies in the optical regime, extrapolating from what is already known about galaxies at z similar or equal to 3. This prediction is consistent with the results of nearly all known searches for objects at z similar or equal to 6, giving confidence that we may use it to plan optimal combination of survey depth and sky coverage in searching for such objects. We suggest that the most efficient strategy with existing ground-based facilities is to do medium-depth (m(AB) similar or equal to 24.0-24.5 mag), wide-field (a couple of square degrees) survey using a wide-field camera at a 4 m class telescope. As the predicted surface density at this brightness level is very sensitive to the value of L-*, the result of such a survey can be easily used to constrain the luminosity evolution from z similar or equal to 3 to 6.
