2005ApJ...624L..21B

We present Gemini integral-field unit spectroscopy and Hubble Space Telescope (HST) F435W- and F814W-band images of a newly discovered four-image gravitational lens, SDSS J140228.22+632133.3 (hereafter SDSSJ1402). The system is the first of 49 spectroscopically selected gravitational lens candidates to be imaged with the Advanced Camera for Surveys Wide-Field Channel on board HST as part of a Snapshot Survey program designed to expand the sample of known gravitational lenses amenable to detailed photometric, lensing, and dynamical studies. The lens is an r=17.00±0.05 elliptical galaxy at a redshift of z_l=0.2046±0.0001, with a luminosity-weighted stellar velocity dispersion of 267±17 km/s within a 3"-diameter aperture. Multiple emission lines place the faint lensed source galaxy at a redshift of z_s=0.4814±0.0001. The best-fitting singular isothermal ellipsoid lens model has an Einstein radius b=1".35±0".025 (or 4.9±0.2 h^–1₆₅kpc), corresponding to an enclosed mass of (30.9±1.1)x10¹⁰ h^–1₆₅M_☉and a rest-frame B-band mass-to-light ratio of 8.1±0.5 h₆₅times solar within the same region. By calculating an expected stellar mass-to-light ratio for SDSSJ1402 using a local universe value of 7.3±2.1 h₆₅and the measured evolution of the fundamental plane, we estimate the fraction of luminous matter within the Einstein radius to be 0.64±0.22: stellar mass is dominant, but some dark matter appears to be required even at this small scale of roughly one-half effective radius.