Key points are not available for this paper at this time.
We report a significant detection of weak, tangential distortion of the images of cosmologically distant, faint galaxies due to gravitational lensing by foreground galaxies. A mean image polarisation of =0. 011 0. 006 is measured for 3202 pairs of source galaxies with magnitudes 23< r 24 and lens galaxies with magnitudes 20 r 23. The signal remains strong for lens-source separations 90'', consistent with quasi-isothermal galaxy halos extending to large radii (100h^-1 kpc). Our observations thus provide the first evidence from weak gravitational lensing of large scale dark halos associated with individual galaxies. The observed polarisation is also consistent with the signal expected on the basis of simulations incorporating measured properties of local galaxies and modest extrapolations of the observed redshift distribution of faint galaxies. From the simulations we derive a best-fit halo circular velocity of V 220 km/s and characteristic radial extent of s 100h^-1 kpc. Our best-fit halo parameters imply typical masses for the lens galaxies within a radius of 100h^-1 kpc on the order of 1. 0^+1. 1-₀. ₇ 10^12h^-1 M_, in good agreement with recent dynamical estimates of the masses of local spiral galaxies. This is particularly encouraging as the lensing and dynamical mass estimators rely on different sets of assumptions. Contamination of the gravitational lensing signal by a population of tidally distorted satellite galaxies can be ruled out with reasonable confidence. The prospects for corroborating and improving this measurement seem good, especially using deep HST archival data.
Brainerd et al. (Fri,) studied this question.