Statistics of dark matter haloes expected from weak lensing surveys

The distortion of the images of faint high-redshift galaxies can be used to probe the intervening mass distribution. This weak gravitational lensing e ffect has been used recently to study the (projected) mass distribution of several clusters at intermediate and high redshifts. In addition, the weak lensing effect can be employed to detect (dark) matter concentrations in th e Universe, based on their mass properties alone. Thus it is feasible to ob tain a mass-selected sample of 'clusters', and thereby probe the full range of their mass-to-light ratios. We study the expected number density of suc h haloes that can be detected in ongoing and future deep wide-field imaging surveys, using the number density of haloes as predicted by the Press-Sche chter theory, and modelling their mass profile by the 'universal' density p rofile found by Navarro, Frank gr White. We find that in all cosmological m odels considered, the number density of haloes with a signal-to-noise ratio larger than 5 exceeds 10 per square degree. With the planned MEGACAM imagi ng survey of similar to 25 deg(2), it will be easily possible to distinguis h between the most commonly discussed cosmological parameter sets.