Gravitational arcs as cosmological and astrophysical probes: the case of Stripe 82

Gravitational arcs are generated by the strong lensing effect, when the light from a distant galaxy (the source) is deflected by a galaxy or galaxy cluster (the lens) in its way across the Universe towards us. These arcs can provide powerful probes of the sources (through the strong magnification, acting as “gravitational telescopes”), the lenses (constraining their matter content), the large-scale geometry of the Universe (providing limits on cosmological models), and gravity itself (probing alternatives to General Relativity). However, systems with gravitational arcs are rare and thus require wide-field surveys of the sky to be identified. In addition, most astrophysical and cosmological applications of arcs require information on multiple bands: spectroscopy of the lens and source (ideally spatially resolved) and photometric information on a wide range of wavelengths. In this talk we describe a region in the sky that fulfills these two requirements: the so-called SDSS Stripe 82 field, a ~ 200 sq-deg stripe in the celestial equatorial region. This region has an impressive multi-wavelength coverage, from radio to X-rays, in addition to a dense spectroscopic coverage from various surveys. In this contribution, we describe the search for gravitational arcs in Stripe 82, where about 50 systems were found, and present a few analyses of selected systems. We also discuss progresses on controlling the several sources of systematics for turning strong lenses into precision probes of cosmology and astrophysics.