2004ApJ...610..686G

Gravitational lenses that produce multiple images of background quasars can be an invaluable cosmological tool. Deriving cosmological parameters, however, requires modeling the potential of the lens itself. It has been estimated that up to a quarter of lensing galaxies are associated with a group or cluster that perturbs the gravitational potential. Detection of X-ray emission from the group or cluster can be used to better model the lens. We report on the first detection in X-rays of the group associated with the lensing system PG 1115+080 and the first X-ray image of the group associated with the system B1422+231. We find a temperature and rest-frame luminosity of 0.8^+0.1_–0.1keV and 7⁺²_–2x10⁴² ergs/s, respectively, for PG 1115+080 and 1.0^+∞_–0.3keV and 8⁺³_–3x10⁴² ergs/s, respectively, for B1422+231. We compare the spatial and spectral characteristics of the X-ray emission with the properties of the group galaxies, with lens models, and with the general properties of groups at lower redshift.