11260(  1) - 03/30/07 11:13  - [  1]

                  HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 11260

Version: 1    Check-in Time: 30-Mar-2007 15:13:32       STScI Edit Number: 0

Title
Galaxy Shapes and Gravitational Lensing
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Type             Cycle     Parallel Pointing Tolerance
AR               16        <none>
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Investigators
                                                                                     Contact?
    PI: Dr. Charles R. Keeton             Rutgers the State University of New Jersey
   CoI: Ms. Jennifer Van Saders           Rutgers the State University of New Jersey    N
   CoI: Dr. Chien Y. Peng                 Space Telescope Science Institute             N

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Abstract

The mass distributions in gravitational lens galaxies--even just the stellar
components--are almost certainly more complicated that we usually assume. This
probably contributes to the problems with lensing constraints on the Hubble
constant. It might also confound studies of dark matter substructure: we recently
found that edge-on disk components in elliptical lens galaxies can create
"anomalous" flux ratios similar to those often attributed to dark matter
substructure. We propose to critically examine how galaxy shapes affect these
applications of gravitational lensing. We will use real galaxies from the GEMS
(Galaxy Evolution from Morphology and SEDs) survey to construct a large catalog of
mock lenses. Working with mock lenses allows us to perform controlled experiments;
but the power comes from using real galaxies so that we automatically include
structures that are more general than conventional parametric lens models yet are
guaranteed to be realistic. We will use the catalog of mock lenses to determine
whether the observed incidence of anomalous flux ratios can be explained by "disky"
lens galaxies or requires dark matter substructure. In doing so, we will derive new
constraints on the amount of dark matter substructure required or allowed by
gravitational lensing, which realistically account for the complexity in galaxy
(stellar) mass distributions. We will also use the mock lenses to provide the first
objective calibration of non-parametric lens models.
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