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Session 59 - Relativistic Astrophysics.
Oral session, Thursday, January 08
Monroe,
The CfA-Arizona Space Telescope LEns Survey (CASTLES) is observing all the known small-separation gravitational lenses with HST at V,R, and H bands. This survey will: identify a subset of clean lens systems where a time-delay may provide a competitive measurement of H_0; obtain photometric redshift estimates for the lenses, thus greatly improving constraints on the cosmological constant; measure directly the M/L ratio for lens galaxies out to z\sim1, thus providing constraints on galaxy evolution; compare the dark matter and stellar light distributions to constrain their structure and shape; and probe the interstellar medium in distant galaxies using differential extinction between the lens images. NICMOS observations are under way, and WFPC2 observations will be completed before the end of Cycle 7. We will present highlights of the NICMOS imaging of several of the lens systems. Our NICMOS observations have revealed Einstein rings connecting the lensed images in B1608+656 and B1936+666. In B1600+434, we find a nearly edge-on lensing galaxy between two images of the background source. In general, the NICMOS observations yield the highest S/N images of the lens galaxies to date.
