Modelling The First Probable Two Plane Lens System B2114+022: Reproducing Two Compact Radio Cores A, D

Abstract

We test possible lensing scenarios of the JVAS system B2114+022, in which two galaxies at different redshifts (``G1'' at $z_1 = 0.3157$ and ``G2'' at $z_2 = 0.5883$) are found within 2 arcseconds of quadruple radio sources. For our investigation, we use possible lensing constraints derived from a wealth of data on the radio sources obtained with VLA, MERLIN, VLBA and EVN as well as HST imaging data on the two galaxies, which are presented in Augusto et al. In the present study, we focus on reproducing the widest separated, observationally similar radio components A and D as lensed images. We first treat G2 (which is the more distant one from the geometric centre) as a shear term, and then consider two plane lensing explicitly including G2's potential at the $z_2$ plane as the first case of two plane lens modelling. Our modelling results not only support the hypothesis that the system includes gravitationally lensed images of a higher redshift extragalactic object, but they also show that the explicit inclusion of G2's potential at the second lens plane is necessary in order to fit the data with astrophysically plausible galaxy parameters. Finally, we illustrate a natural consequence of a two-plane lens system, namely the prediction of distortion as well as shift and stretching of G2's isophotes by G1's potential, which can in principle be measured by subtracting out G1's light distribution in a high S/N and good angular resolution image, especially a multi-colour one.