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# A new Einstein Cross gravitational lens of a Lyman-break galaxy

 Bettoni, D., Falomo, R., Scarpa, R., Negrello, Mattia, Omizzolo, A., Corradi, R. L. M., Reverte, D. and Vulcani, B. 2019. A new Einstein Cross gravitational lens of a Lyman-break galaxy. Astrophysical Journal Letters 873 (2) , L14. 10.3847/2041-8213/ab0aeb

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## Abstract

We report the study of an "Einstein Cross" configuration first identified in a set of HST images by Cerny et al. Deep spectroscopic observations obtained at the Spanish 10.4 m Gran Telescopio Canarias telescope, allowed us to demonstrate the lens nature of the system, that consists of a Lyman-break galaxy (LBG), not a quasi-stellar object as is usually the case, at z = 3.03 lensed by a galaxy at z = 0.556. Combining the new spectroscopy with the archival HST data, it turns out that the lens is an elliptical galaxy with M V = −21.0, effective radius 2.8 kpc, and stellar velocity dispersion σ = 208 ± 39 km s−1. The source is an LBG with Lyα luminosity ~L* at that redshift. From the modeling of the system, performed by assuming a singular isothermal ellipsoid (SIE) with external shear, we estimate that the flux source is magnified about 4.5 times, and the velocity dispersion of the lens is ${\sigma }_{\mathrm{SIE}}={197.9}_{-1.3}^{+2.6}$ km s−1, in good agreement with the value derived spectroscopically. This is the second case known of an Einstein cross of an LBG.

Item Type: Article Publication Published Physics and Astronomy American Astronomical Society 2041-8205 11 March 2019 27 February 2019 12 Mar 2019 11:42 http://orca.cf.ac.uk/id/eprint/120502

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