Adaptive optics imaging of the class gravitational lens system B1359+154 with the Canada-France-Hawaii Telescope

We present adaptive optics imaging of the CLASS gravitational lens system B 1359+154 obtained with the Canada-France-Hawaii Telescope (CFHT) in the inf rared K band. The observations show at least three brightness peaks within the ring of lensed images, which we identify as emission from multiple lens ing galaxies. The results confirm the suspected compound nature of the lens , as deduced from preliminary mass modeling. The detection of several addit ional nearby galaxies suggests that B1359+154 is lensed by the compact core of a small galaxy group. We attempted to produce an updated lens model bas ed on the CFHT observations and new 5 GHz radio data obtained with the MERL IN array, but there are too few constraints to construct a realistic model at this time. The uncertainties inherent with modeling compound lenses make B1359+154 a challenging target for Hubble constant determination through t he measurement of differential time delays. However, time delays will offer additional constraints to help pin down the mass model. This lens system t herefore presents a unique opportunity to directly measure the mass distrib ution of a galaxy group at intermediate redshift.