1994A&A...286..357K

We investigate simple gravitational lens models for the recently discovered quadruple QSO B1422+231. The image configuration in this multiple QSO system indicates that the gravitational deflector has a considerable ellipticity; we therefore explore lensing models based on elliptical mass distributions. Employing a simple fitting procedure, we show that (1) our models cannot satisfactorily account for the details of the image configuration, in particular, the flux ratios are difficult to reproduce; (2) Our best model is a combination of an elliptical deflector and externally applied shear; the direction of the shear is in accordance with the position of two galaxies detected near the QSO images, and may well be produced by them. If this interpretation is correct, our best model is in fact quite similar to the model of Hogg & Blandford, except that we account for the ellipticity of the main deflector, which reduces the mass of the nearby galaxies to produce the necessary shear. The fact that the models do not improve if the position of the lens center is allowed to vary from its observed position is a strong argument in favour of it being indeed the main lensing galaxy.