Sunday, May 19, 2013

1305.3608 (Matteo Maturi et al.)

Multi-color detection of gravitational arcs: method and new candidates    [PDF]

Matteo Maturi, Sebastian Mizera, Gregor Seidel
Strong gravitational lensing provides fundamental insights in the understanding of the dark matter distribution in massive galaxies, galaxy clusters and the background cosmology. Despite their importance, the number of gravitational arcs discovered so far is small. The urge for more complete, large samples and unbiased methods of selecting candidates is rising. A number of methods for the automatic detection of arcs have been proposed in the literature, but large amounts of spurious detections retrieved by these methods forces observers to visually inspect thousands of candidates per square degree in order to clean the samples. This approach is largely subjective and requires a huge amount of eye-ball checking, especially considering the actual and upcoming wide field surveys, which will cover thousands of square degrees. In this paper we study the statistical properties of colors of gravitational arcs. We found that most of them lie in a relatively small region of the color-color diagram (g'-r',r'-i'). We support this observational evidence by studying lensing cross section, which peaks for sources at redshift z~1, where the source-galaxy population is dominated by galaxies with large star forming regions and hence well defined colors. The use of this distinctive feature, in combination with an automatic arcfinder, reduces sample contamination by a factor of 6-7. We tested the performance of the method against 37 deg^2 of the CARS survey, detecting 73 new arc candidates.
View original: http://arxiv.org/abs/1305.3608

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