Detection of (dark) matter concentrations via weak gravitational lensing

Abstract

A method for the detection of dark matter concentrations in the Universe is proposed, based on the image distortion of faint background galaxies caused by these dark haloes. The weight function of the aperture mass measures is optimized with respect to the signal-to-noise ratio for approximately isothermal mass proilles. Analytic estimates for the signal-to-noise ratio are derived, and numerical simulations are used to show that dark matter haloes with velocity dispersion u ;:::: 600 km S-1 can be reliably detected. The effect of seeing and of an anisotropic point-spread function are investigated and shown to yield only slightly reduced values for the signal-to-noise ratio. This method, which is easy to apply to wide-field deep images, offers the opportunity to obtain a mass-selected sample of haloes, and to study their cosmological density, without any assumptions about their mass-to-light ratio.