IAU01833
Presentation type requested: EITHER
MULTIPLE WEAK DEFLECTIONS IN THE HDF-NORTH
Tereasa Brainerd
Boston University
On scales from those of galaxies, through to the large-scale structure of the universe, weak lensing of distant galaxy images by mass along the line of sight has become a powerful method for mapping dark matter. A complicating effect of weak lensing by galaxies (a.k.a. galaxy-galaxy lensing) is that it is not, in general, a single deflection problem. Instead, sources with redshifts of order 1 have usually been lensed at a comparable level by 2 or more foreground galaxies. This affects the interpretation of galaxy-galaxy lensing signals and it induces correlated ellipticities in the source images. The latter must be accounted for in small-angle measurements of cosmic shear (i.e., weak lensing by large-scale structure). Here the HDF-North will be used to demonstrate the effects of multiple deflections on the galaxy-galaxy lensing signal and on measurements of cosmic shear on very small scales. The effects are largely independent of the cosmological parameters, but are very sensitive to the characteristic potentials of the halos of L* galaxies. A discussion of the angular scales over which the details of galaxy-galaxy lensing are unlikely to affect the cosmic shear signal will be presented.
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