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

V. Belokurov (1); N.W.Evans (1); A.Moiseev (2); L.J. King (1); P.C.; Hewett (1); M. Pettini (1); L. Wyrzykowski (1,4); R.G. McMahon (1); M.C.; Smith (1); G. Gilmore (1); S.F. Sanchez (3); A. Udalski (4); S. Koposov (5),; D.B. Zucker (1); C.J. Walcher (6) ((1) Cambridge; (2) SAO; (3) Calar Alto,; (4) Warsaw; (5) MPIA; (6) Marseille)

arXiv:0706.2326·astro-ph·November 13, 2009

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

V. Belokurov (1), N.W.Evans (1), A.Moiseev (2), L.J. King (1), P.C., Hewett (1), M. Pettini (1), L. Wyrzykowski (1,4), R.G. McMahon (1), M.C., Smith (1), G. Gilmore (1), S.F. Sanchez (3), A. Udalski (4), S. Koposov (5),, D.B. Zucker (1), C.J. Walcher (6) ((1) Cambridge, (2) SAO

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TL;DR

This paper reports the discovery of a nearly complete Einstein ring around a massive luminous red galaxy, providing insights into dark matter distribution and high-redshift star-forming galaxies.

Contribution

It presents the first detailed analysis of an Einstein ring around a giant LRG, including spectroscopic data and mass estimation, advancing gravitational lensing studies.

Findings

01

The Einstein ring has a diameter of 10 arcseconds.

02

The lens galaxy has a velocity dispersion over 400 km/s.

03

The lens galaxy's mass within the Einstein radius is approximately 5 x 10^12 solar masses.

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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