Discovery of two gravitationally lensed quasars in the Dark Energy Survey

Adriano Agnello, Tommaso Treu, Fernanda Ostrovski, Paul L. Schechter, Elizabeth J. Buckley-Geer, Huan Lin, Matthew W. Auger, Frederic Courbin, Christopher D. Fassnacht, Josh Frieman, Nikolay Kuropatkin, Philip J. Marshall, Richard G. McMahon, Georges Meylan, Anupreeta More, Sherry H. Suyu, Cristian E. Rusu, David Finley, Tim Abbott, Filipe B. AbdallaSahar Allam, James Annis, Manda Banerji, Aurélien Benoit-Lévy, Emmanuel Bertin, David Brooks, David L. Burke, Aurelio Carnero Rosell, Matias Carrasco Kind, Jorge Carretero, Carlos E. Cunha, Chris B. D'Andrea, Luiz N. da Costa, Shantanu Desai, Thomas Diehl, Jörg P. Dietrich, Peter Doel, Tim F. Eifler, Juan Estrada, Angelo Fausti Neto, Brenna Flaugher, Pablo Fosalba, David W. Gerdes, Daniel Gruen, Gaston Gutierrez, Klaus Honscheid, David J. James, Kyler Kuehn, Ofer Lahav, Marco Lima, Marcio A. G. Maia, Marisa March, Jennifer L. Marshall, Paul Martini, Peter Melchior, Christopher J. Miller, Ramon Miquel, Robert C. Nichol, Ricardo Ogando, Andres A. Plazas, Kevin Reil, Kathy Romer, Aaron Roodman, Masao Sako, Eusebio Sanchez, Basilio Santiago, Vic Scarpine, Michael Schubnell, Ignacio Sevilla-Noarbe, Chris Smith, Marcelle Soares-Santos, Flavia Sobreira, Eric Suchyta, Molly E. C. Swanson, Gregory Tarle, Jon Thaler, Douglas Tucker, Alistair R. Walker, Risa H. Wechsler, Yuanyuan Zhang

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Abstract

We present spectroscopic confirmation of two new lensed quasars via data obtained at the 6.5m Magellan/Baade Telescope. The lens candidates have been selected from the Dark Energy Survey (DES) and WISE based on their multi-band photometry and extended morphology in DES images. Images of DES J0115-5244 show two blue point sources at either side of a red galaxy. Our long-slit data confirm that both point sources are images of the same quasar at $z_{s}=1.64.$ The Einstein Radius estimated from the DES images is $0.51$". DES J2200+0110 is in the area of overlap between DES and the Sloan Digital Sky Survey (SDSS). Two blue components are visible in the DES and SDSS images. The SDSS fiber spectrum shows a quasar component at $z_{s}=2.38$ and absorption compatible with Mg II and Fe II at $z_{l}=0.799$, which we tentatively associate with the foreground lens galaxy. The long-slit Magellan spectra show that the blue components are resolved images of the same quasar. The Einstein Radius is $0.68$" corresponding to an enclosed mass of $1.6\times10^{11}\,M_{\odot}.$ Three other candidates were observed and rejected, two being low-redshift pairs of starburst galaxies, and one being a quasar behind a blue star. These first confirmation results provide an important empirical validation of the data-mining and model-based selection that is being applied to the entire DES dataset.
Original languageEnglish
Pages (from-to)1260-1265
JournalMonthly Notices of the Royal Astronomical Society
Volume454
Issue number2
DOIs
Publication statusPublished - 1 Oct 2015

Keywords

  • astro-ph.GA
  • astro-ph.CO
  • gravitational lensing: strong
  • quasars: emission lines
  • methods: observational
  • methods: statistical
  • RCUK
  • STFC

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