SDSS J140228.22+632133.3: A New Spectroscopically Selected Gravitational Lens

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Abstract
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 zl = 0.2046 ± 0.0001, with a luminosity-weighted stellar velocity dispersion of 267 ± 17 km s-1 within a 3''-diameter aperture. Multiple emission lines place the faint lensed source galaxy at a redshift of zs = 0.4814 ± 0.0001. The best-fitting singular isothermal ellipsoid lens model has an Einstein radius b = 135 ± 0025 (or 4.9 ± 0.2 h kpc), corresponding to an enclosed mass of (30.9 ± 1.1) × 1010 h M☉ and a rest-frame B-band mass-to-light ratio of 8.1 ± 0.5 h65 times 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 h65 and 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.
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