* Astronomy

Title: Adaptive Optics Observations of B0128+437: A Low-Mass, High-Redshift Gravitational Lens
Authors: David J. Lagattuta (1), Matthew W. Auger (2), Christopher D. Fassnacht (1) ((1) UC Davis, (2) UC Santa Barbara)
(Version v2)

We use high-resolution adaptive optics (AO) imaging on the Keck II telescope to study the gravitational lens B0128+437 in unprecedented detail, allowing us to resolve individual lensed quasar components and, for the first time, detect and measure properties of the lensing galaxy. B0128+437 is a small separation lens with known flux-ratio and astrometric anomalies. We discuss possible causes for these anomalies, including the presence of substructure in the lensing galaxy, propagation effects due to dust and a turbulent interstellar medium, and gravitational microlensing. This work on B0128 demonstrates that AO will be an essential tool for studying the many new small-separation lenses expected from future surveys.

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