Multiple Weak Deflections in Galaxy-Galaxy Lensing

Abstract

The frequency and effects of multiple weak deflections in galaxy-galaxy lensing are investigated via Monte Carlo simulations. The lenses in the simulations are galaxies with known redshifts and known rest-frame blue luminosities. The frequency of multiple deflections above a given threshold shear value is quantified for discrete source redshifts, as well as for a set of sources that are broadly distributed in redshift space. In general, the closest lens in projection on the sky is not the only lens for a given source. In addition, ~50% of the time the closest lens is not the most important lens for a given source. Compared to a naive single-deflection calculation in which only the lensing due to the closest weak lens is considered, a full multiple-deflection calculation yields a higher net shear for individual sources, as well as a higher mean tangential shear around the lens centers. The full multiple-deflection calculation also shows that galaxy-galaxy lensing may contribute a substantial amount to cosmic shear on small angular scales. The degree to which galaxy-galaxy lensing contributes to the small-scale cosmic shear is, however, quite sensitive to the mass adopted for the halos of L_B* galaxies. Changing the halo mass by a factor of ~2.5 changes the contribution of galaxy-galaxy lensing to the cosmic shear by a factor of ~3 on scales of order 1 arcmin. The contribution of galaxy-galaxy lensing to cosmic shear decreases rapidly with angular scale and extrapolates to zero at scales of order 5 arcmin. This last result is roughly independent of the halo mass and suggests that for scales greater than about 5 arcmin, cosmic shear is insensitive to the details of the gravitational potentials of large galaxies.

accepted for publication in ApJ; 35 pages, 15 figures; full text with high-resolution Figure 1 available at http://firedrake.bu.edu/preprints/preprints.html

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Cited by in corpus (8)

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• Halo Shapes From Weak Lensing: The Impact of Galaxy--Halo Misalignment
• CFHTLenS: Weak lensing constraints on the ellipticity of galaxy-scale matter haloes and the galaxy-halo misalignment
• Galaxy-Galaxy Lensing by Non-Spherical Haloes I:Theoretical Considerations
• Weak lensing mass estimates of galaxy groups and the line-of-sight contamination
• Exotic Image Formation in Strong Gravitational Lensing by Clusters of Galaxies -- III: Statistics with HUDF