Cristina Furlanetto, Basilio X. Santiago, Martin Makler, Eduardo S. Cypriano, Gabriel B. Caminha, Maria Elidaiana da Silva Pereira, Angelo Fausti Neto, Juan Estrada, Huan Lin, Jiangang Hao, Timothy A. McKay, Luiz Nicolaci da Costa, Marcio A. G. Maia
We present the first results of the SOAR Gravitational Arc Survey (SOGRAS). The survey imaged 51 clusters in two narrow redshift intervals centered at $z=0.27$ and $z=0.55$, targeting the richest clusters in each interval. Images were obtained in the $g'$, $r'$, and $i'$ bands using the SOAR Optical Imager (SOI), with a median seeing of 0.82", 0.74", and 0.69", respectively, in these filters. Most of the survey clusters are located within the Sloan Digital Sky Survey (SDSS) Stripe 82 region and all of them are in the SDSS footprint. Photometric calibration was therefore performed using SDSS stars located in our SOI fields. We reached for galaxies in all fields the detection limits of $g \sim 23$, $r \sim 22.5$, and $i \sim 22$ for $S/N=3$. As a by-product of the image processing, we generated a source catalog with 21280 entries, the vast majority of which are galaxies, where we list their positions, magnitudes, and shape parameters. We compared our galaxy shape measurements to those of local galaxies and concluded that they were not strongly affected by seeing. From the catalog data, we are able to identify a red sequence of galaxies in most clusters in the lower $z$ range. We found 16 gravitational arc candidates around 8 clusters in our sample. They tend to be bluer than the central galaxies in the lensing cluster. A preliminary analysis indicates that $\sim 10%$ of the clusters have arcs around them, with a possible indication of a larger efficiency associated to the high-$z$ systems when compared to the low-$z$ ones. Deeper follow-up images with Gemini strengthen the case for the strong lensing nature of the candidates found in this survey.
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http://arxiv.org/abs/1210.4136
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