B1422+231: The influence of mass substructure on strong lensing

¹ Institut für Astrophysik und Extraterrestrische Forschung, Auf dem Hügel 71, 53121 Bonn, Germany
² Steward Observatory, 933 North Cherry Avenue, Tucson, AZ 85721, USA
³ Max Planck Institut für Astrophysik, Karl-Schwarzschild Str. 1, 85748 Garching bei München, Germany
⁴ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany

Corresponding author: M. Bradač, marusa@astro.uni-bonn.de

Received: 4 December 2001
Accepted: 9 April 2002

Abstract

In this work we investigate the gravitationally lensed system B1422+231. High-quality VLBI image positions, fluxes and shapes as well as an optical HST lens galaxy position are used. First, two simple and smooth models for the lens galaxy are applied to fit observed image positions and fluxes; no even remotely acceptable model was found. Such models also do not accurately reproduce the image shapes. In order to fit the data successfully, mass substructure has to be added to the lens, and its level is estimated. To explore expectations about the level of substructure in galaxies and its influence on strong lensing, N-body simulation results of a model galaxy are employed. By using the mass distribution of this model galaxy as a lens, synthetic data sets of different four image system configurations are generated and simple lens models are again applied to fit them. The difficulties in fitting these lens systems turn out to be similar to the case of some real gravitationally lensed systems, thus possibly providing evidence for the presence and strong influence of substructure in the primary lens galaxy.