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

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 z_l=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 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^-1₆₅ kpc), corresponding to an enclosed mass of (30.9+/-1.1)×10¹⁰ h^-1₆₅ M_solar 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.

Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at STScI, which is operated by AURA, Inc., under NASA contract NAS 5-26555. These observations are associated with program 10174. Support for program 10174 was provided by NASA through a grant from STScI.

Also based on observations obtained under program GN-2004A-Q-5 at the Gemini Observatory, which is operated by AURA, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the NSF (US), the PPARC (UK), the NRC (Canada), CONICYT (Chile), the ARC (Australia), CNPq (Brazil), and CONICET (Argentina).