Adaptive Optics Observations of B0128+437: A Low-Mass, High-Redshift Gravitational Lens

TL;DR

This study employs high-resolution adaptive optics imaging to analyze the gravitational lens B0128+437, revealing detailed properties of the lensing galaxy and discussing anomalies potentially caused by substructure, dust, or microlensing.

Contribution

First detailed AO imaging of B0128+437, providing insights into lensing anomalies and demonstrating AO's importance for future small-separation lens studies.

Findings

Resolved individual quasar components.

Detected and measured lensing galaxy properties.

Discussed potential causes for flux-ratio and astrometric anomalies.

Abstract

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.