The CASSOWARY spectroscopy survey: A new sample of gravitationally lensed galaxies in SDSS

Abstract

Bright gravitationally lensed galaxies provide our most detailed view of galaxies at high redshift. The very brightest (r < 21) systems enable high spatial and spectral resolution measurements, offering unique constraints on the outflow energetics, metallicity gradients and stellar populations in high-redshift galaxies. Yet as a result of the small number of ultrabright z ≃ 2 lensed systems with confirmed redshifts, most detailed spectroscopic studies have been limited in their scope. With the goal of increasing the number of bright lensed galaxies available for detailed follow-up, we have undertaken a spectroscopic campaign targeting wide separation (≳3 arcsec) galaxy-galaxy lens candidates within the Sloan Digital Sky Survey (SDSS). Building on the earlier efforts of our Cambridge and Sloan Survey Of Wide Arcs in Thesky survey, we target a large sample of candidate galaxy-galaxy lens systems in SDSS using a well-established search algorithm which identifies blue arc-like structures situated around luminous red galaxies. In this paper, we present a new redshift catalogue containing 29 lensed sources in SDSS confirmed through spectroscopic follow-up of candidate galaxy-galaxy lens systems. Included in this new sample are two of the brightest galaxies (r=19.6 and 19.7) known at z ≃ 2, a low metallicity (12 + log (O/H) ≃ 8.0) extreme nebular line emitting galaxy at z = 1.43, and numerous systems for which detailed follow-up will be possible. The source redshifts span 0.9