Modelling the first probable two-plane lens system B2114+022: reproducing two compact radio cores A and D

We test possible lensing scenarios of the WAS system B2114+022, in which tw o galaxies at different redshifts ('G1' at z(1) = 0.3157 and 'G2' at z(2) = 0.5883) are found within 2 arcsec of quadruple radio sources. For our inve stigation, we use possible lensing constraints derived from a wealth of dat a on the radio sources obtained with VLA, MERLIN, VLBA and EVN as well as H ST imaging data on the two galaxies, which were presented recently in Augus to et al. In the present study, we focus on reproducing the widest separate d, observationally similar radio components A and D as lensed images. We fi rst 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 inclu des gravitationally lensed images of a higher-redshift extragalactic object , but they also show that the explicit inclusion of G2's potential at the s econd 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 prin ciple be measured by subtracting out G1's light distribution in an image of high signal-to-noise ratio and good angular resolution, especially a multi colour one.