11 5 × 10 5 R-band image obtained from stacking 60 hr of the best-quality images in the COSMOGRAIL monitoring. The lens system is marked by the box near the center. Galaxies (stars) in the field are indicated by solid (dashed) circles. The radius of the solid circle is proportional to the flux of the galaxy. X-ray map from Chartas et al. (2009) is overlaid on the image within the dashed box. The concentrations of mass structures to the east of the lens are consistent with the modeled external shear and convergence gradient directions.