Mass and Environment of a Low-Redshift Gravitational Lens Galaxy

We propose EPIC and Optical/UV Monitor observations of the lowredshiftstronglensing elliptical galaxy ESO325G004, and its surrounding group AbellS0740. The principal aims of the observation are (1) to test for the presence ofextended intragroup gas; (2) to measure a gas temperature for both the centralgalaxy component and the intragroup medium. The Xray results will help toestablish the contribution of the group potential to the lensing mass, andcomplement lensing and dynamical mass estimates for the system at smaller radii.Simultaneous UV imaging with the OM will exploit the colour contrast against thered lens galaxy, to constrain the properties of the starforming backgroundsource. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]