Multifrequency radio images of the Einstein ring gravitational lens MG 1131+0456

Abstract

We present multifrequency radio images of the Einstein ring gravitational lens system, MG 1131+0456, acquired with the Very Large Array (VLA) telescope. Continuum data at 5, 8, 15, and 22 GHz are presented, ranging in resolution from 0.09 sec to 0.39 sec. Linearly polarized emission, detected in the 5 and 8 GHz images, reveals complex structure that will provide strong constraints on lens models. We find evidence for flat spectrum components at the positions of the doubly imaged compact components, suggesting that the compact objects are radio cores and that the possibility of variability should not be excluded. At 8 GHz, a new unresolved component near the center of the ring is detected; it is likely to be the third and fifth images of parts of the background source. Varying degrees of Faraday rotation, with large rotation measure, are detected across the source. Variations in depolarization are also seen, and can be reconstructed by a model consisting of a lens with an elliptical gravitational potential and a radio source with a core, a one-sided jet, and two extended radio lobes.