Cluster mass profiles from weak lensing: The influence of substructure

The tidal gravitational field of a cluster distorts the shapes of backgroun d galaxies. This signature can be used to place constraints on the mass pro file of the cluster, using a maximum likelihood analysis to find the best-f it parameterised model. In Schneider et al. (2000) and King & Schneider (20 01) we investigated how accurately parameters can be obtained, concentratin g on smooth profiles. Here, we consider a realistic model for substructure in a cluster (from N-body simulations), in order to see what influence this has on the recovery of parameters. We find that for a typical cluster at z (d) = 0.2, the presence of substructure increases the error on parameters r ecovered from weak lensing data by approximate to3%. Even doubling the subs tructure amplitude induces only a approximate to 10% increase in the parame ter dispersion: this bodes well for our method.