A Study of Gravitational Lens Chromaticity with the Hubble Space Telescope

Abstract

We report Hubble Space Telescope observations of six gravitational lenses with the Advanced Camera for Surveys. We measured the flux ratios between the lensed images in seven filters from 8140 Å to 2200 Å. In three of the systems, HE0512-3329, B1600+434, and H1413+117, we were able to construct UV extinction curves partially overlapping the 2175 Å feature and characterize the properties of the dust relative to the Galaxy and the Magellanic Clouds. In HE1104-1804, we detect chromatic microlensing and use it to study the physical properties of the quasar accretion disk. For a Gaussian model of the disk exp (- r ²/2r ² _s ), scaling with wavelength as r_s vpropλ ^p , we estimate r_s (λ3363) = 4⁺⁴ _{- 2} (7 ± 4) light days and p = 1.1 ± 0.6 (1.0 ± 0.6) for a logarithmic (linear) prior on r_s . The remaining two systems, FBQ0951+2635 and SBS1520+530, yielded no useful estimates of extinction or chromatic microlensing.

Based on observations made with the NASA/ESA Hubble Space Telescope. The Space Telescope Science Institute is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.