IMPROVING THE ACCURACY OF MASS RECONSTRUCTIONS FROM WEAK LENSING - LOCAL SHEAR MEASUREMENTS

Different options can be used in order to measure the shear from obser vations in the context of weak lensing. Here we introduce new methods where the isotropy assumption for the distribution of the source galax ies is implemented directly on the observed quadrupole moments. A quan titative analysis of the error associated with the finite number of so urce galaxies and with their ellipticity distribution is provided, app licable even when the shear is not weak. Monte Carlo simulations based on a realistic sample of source galaxies show that our procedure gene rally leads to errors approximate to 25% smaller than those associated with the standard method of Kaiser and Squires (1993).