Weak Galaxy-Galaxy Lensing in HST DATA

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We expand on the work of Brainerd, Blandford & Smail (1996) (BBS), using a larger archival WFPC-2 dataset including many galaxy redshifts. It is clear from our data that the ellipticity distribution of images changes substantially with observed magnitude (figure 1, left) which is shown by simulations to be mainly the result of detection effects. We have detected a lensing signal, using a similar selection method to BBS and are also implementing a maximum likelihood method to constrain halo parameters. Using simulations, we show in figure 1 (right) that the signal is consistant with typical halo velocity dispersions of σ^∗ ∼ 70–100 kms⁻¹ However, the radial extent of the halos is less well constrained.