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Published July 2, 2003 | Published + Submitted
Journal Article Open

LBQS 1429-0053: A binary quasar rather than a lensed quasar

Abstract

Very deep ESO/VLT FORS1 and ISAAC images, as well as HST NICMOS2 data are used to infer the nature of the quasar pair LBQS 1429-0053 A and B, either a binary quasar or a doubly-imaged lensed quasar. Direct search of a putative lensing galaxy is unsuccessful down to R = 27, J = 24, K s = 22.5 and H = 22.5. Moreover, no galaxy overdensity close to the quasar pair is found. A weak shear analysis of the FORS1 R-band 6.8´ x 6.8´ field also fails at detecting any concentration of dark matter more massive than σ = 500 km s^(-1) and weakens the hypothesis of a dark lens. The only sign of a possible lens consists in a group of 5 objects having colors consistent with galaxies at z ~ 1, within a radius of 5" from the quasar pair. Considering this group as the lensing potential does not allow to reproduce the image position and flux ratio of LBQS 1429-0053 A and B. Our deep R-band image shows a blue, previously unknown, extended object at the position of LBQS 1429-0053 A, which is consistent with either being the lensed quasar A host, or being an intervening galaxy at lower redshift. Unless future very deep optical images demonstrate that this object is actually the lensed host of LBQS 1429-0053, we conclude that there is very little evidence for LBQS 1429-0053 being lensed. Therefore, we are led to declare LBQS 1429-0053 A and B a genuine binary quasar.

Additional Information

© 2003 ESO. Received 20 December 2002. Accepted 27 March 2003. We acknowledge the guidance of Andreas Jaunsen in the NICMOS2 data reduction. Micol Bolzonella provided help in the application of the Hyperz software to the present dataset. We are indebted to an anonymous referee for interesting comments. The HST data used in this paper were obtained by the "CfA Arizona Space Telescope LEns Survey'' (CASTLES) collaboration (PI: E. Falco). Cécile Faure acknowledges support from an ESO studentship in Santiago. Frédéric Courbin is supported by Marie Curie grant MCFI-2001-00242. The collaborative grant ECOS/CONICYT CU00U005 between Chile and France is also gratefully acknowledged. Jean-Paul Kneib thanks CNRS for support as well as the ESO Chile visitor program.

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Created:
August 19, 2023
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October 18, 2023