We present new mass models for the gravitational lens system B1938+666 , using multi-wavelength data acquired from Keck adaptive optics ( AO ) and Hubble Space Telescope ( HST ) observations .
These models are the first results from the Strong-lensing at High Angular Resolution Program ( SHARP ) , a project designed to study known quadruple-image and Einstein ring lenses using high-resolution imaging , in order to probe their mass distributions in unprecedented detail .
Here , we specifically highlight differences between AO- and HST -derived lens models , finding that – at least when the lens and source galaxies are both bright and red , and the system has a high degree of circular symmetry – AO-derived models place significantly tighter constraints on model parameters .
Using this improved precision , we infer important physical properties about the B1938+666 system , including the mass density slope of the lensing galaxy ( \gamma = 2.045 ) , the projected dark matter mass fraction within the Einstein radius ( M _ { dark } / M _ { lens } = 0.55 ) , and the total magnification factor of the source galaxy ( \sim 13 ) .
Additionally , we measure an upper-limit constraint on luminous substructure ( M _ { V } > − 16.2 ) , based on the non-detection of bright satellite galaxies in all data sets .
Finally , we utilize the improved image resolution of the AO data to reveal the presence of faint arcs outside of the primary Einstein ring .
The positions and orientations of these arcs raise the intriguing possibility that B1938+666 has a second source galaxy , located at a more distant redshift .
However , future work is needed to verify this hypothesis .