Other
Scientific paper
May 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011aas...21823503g&link_type=abstract
American Astronomical Society, AAS Meeting #218, #235.03; Bulletin of the American Astronomical Society, Vol. 43, 2011
Other
Scientific paper
Gravitational lensing is one of the most stunning confirmations of Einstein's theory of general relativity. In the most extreme cases, distant objects like quasars can be lensed by the mass of intermediate galaxies to produce configurations of multiple images, sometimes as many as six. In particular, we focus on the "fold” lens configuration, where two of the images, mirror images of one another, lay very closely spaced across a critical curve. Since the entire galaxy's mass distribution affects the magnification of the images, the flux ratio of the pair can be used as a tool for investigating substructure.
In the absence of substructure, we would naively expect the two images to be of equal brightness. However, `anomalous’ (non-zero) flux ratios seem to dominate observations of such lens systems. Possible reasons that have been investigated include microlensing, differential absorption by dust, and galaxy substructure. However, we look at yet another possibility for `anomalous’ flux ratios, and one that will allow us to use the lensing galaxy as a microscope: the finite size of the background quasar.
In the present work, we develop a semi-analytic expression for the magnification of images in a multiple-image lens system in which higher order lensing effects (and consequently higher order shape distortions) are taken into account. How the flux ratios will be affected by source size and image positions using this expression will need to be further assessed. In particular, we study where and when the flux ratio deviates from zero for fold lenses. This will ultimately allow us to model the radial color distribution in quasars, giving us new insights into their structure.
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