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arXiv · 0706.2326

The Cosmic Horseshoe: Discovery of an Einstein Ring around a Giant Luminous Red Galaxy

V. Belokurov·N. W. Evans·A. Moiseev·L. J. King·P. C. Hewett·M. Pettini·L. Wyrzykowski·R. G. McMahon·M. C. Smith·G. Gilmore·S. F. Sanchez·A. Udalski·S. Koposov·D. B. Zucker·C. J. Walcher
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Abstract

We report the discovery of an almost complete Einstein ring of diameter 10" in Sloan Digital Sky Survey (SDSS) Data Release 5 (DR5). Spectroscopic data from the 6m telescope of the Special Astrophysical Observatory reveals that the deflecting galaxy has a line-of-sight velocity dispersion in excess of 400 km/s and a redshift of 0.444, whilst the source is a star-forming galaxy with a redshift of 2.379. From its color and luminosity, we conclude that the lens is an exceptionally massive Luminous Red Galaxy (LRG) with a mass within the Einstein radius of 5 x 10^12 solar masses. This remarkable system provides a laboratory for probing the dark matter distribution in LRGs at distances out to 3 effective radii, and studying the properties of high redshift star-forming galaxies.

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V. Belokurov, N. W. Evans, A. Moiseev, L. J. King, P. C. Hewett, M. Pettini, L. Wyrzykowski, R. G. McMahon, M. C. Smith, G. Gilmore, S. F. Sanchez, A. Udalski, S. Koposov, D. B. Zucker, C. J. Walcher. 2007-11-01. The Cosmic Horseshoe: Discovery of an Einstein Ring around a Giant Luminous Red Galaxy. https://doi.org/10.1086/524948

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