The STRong lensing Insights into the Dark Energy Survey (STRIDES) 2017/2018 follow-up campaign: discovery of 10 lensed quasars and 10 quasar pairs Academic Article uri icon

abstract

  • ABSTRACT We report the results of the STRong lensing Insights into the Dark Energy Survey (STRIDES) follow-up campaign of the late 2017/early 2018 season. We obtained spectra of 65 lensed quasar candidates with ESO Faint Object Spectrograph and Camera 2 on the NTT and Echellette Spectrograph and Imager on Keck, confirming 10 new lensed quasars and 10 quasar pairs. Eight lensed quasars are doubly imaged with source redshifts between 0.99 and 2.90, one is triply imaged (DESJ03452545, z= 1.68), and one is quadruply imaged (quad: DESJ00532012, z= 3.8). Singular isothermal ellipsoid models for the doubles, based on high-resolution imaging from SAMI on Southern Astrophysical Research Telescope or Near InfraRed Camera 2 on Keck, give total magnifications between 3.2 and 5.6, and Einstein radii between 0.49 and 1.97 arcsec. After spectroscopic follow-up, we extract multi-epoch grizY photometry of confirmed lensed quasars and contaminant quasar+star pairs from DES data using parametric multiband modelling, and compare variability in each systems components. By measuring the reduced 2 associated with fitting all epochs to the same magnitude, we find a simple cut on the less variable component that retains all confirmed lensed quasars, while removing 94percent of contaminant systems. Based on our spectroscopic follow-up, this variability information improves selection of lensed quasars and quasar pairs from 34-45percent to 5170percent, with most remaining contaminants being star-forming galaxies. Using mock lensed quasar light curves we demonstrate that selection based only on variability will over-represent the quad fraction by 10percent over a complete DES magnitude-limited sample, explained by the magnification bias and hence lower luminosity/more variable sources in quads.

published proceedings

  • MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

altmetric score

  • 7.33

author list (cited authors)

  • Lemon, C., Auger, M. W., McMahon, R., Anguita, T., Apostolovski, Y., Chen, G., ... Walker, A. R.

citation count

  • 31

complete list of authors

  • Lemon, C||Auger, MW||McMahon, R||Anguita, T||Apostolovski, Y||Chen, GC-F||Fassnacht, CD||Melo, AD||Motta, V||Shajib, A||Treu, T||Agnello, A||Buckley-Geer, E||Schechter, PL||Birrer, S||Collett, T||Courbin, F||Rusu, CE||Abbott, TMC||Allam, S||Annis, J||Avila, S||Bertin, E||Brooks, D||Burke, DL||Rosell, A Carnero||Kind, M Carrasco||Carretero, J||Costanzi, M||da Costa, LN||De Vicente, J||Desai, S||Eifler, TF||Flaugher, B||Frieman, J||Garcia-Bellido, J||Gaztanaga, E||Gerdes, DW||Gruen, D||Gruendl, RA||Gschwend, J||Gutierrez, G||Honscheid, K||James, DJ||Kim, A||Krause, E||Kuehn, K||Kuropatkin, N||Lahav, O||Lima, M||Lin, H||Maia, MAG||March, M||Marshall, JL||Menanteau, F||Miquel, R||Palmese, A||Paz-Chinchon, F||Plazas, AA||Roodman, A||Sanchez, E||Schubnell, M||Serrano, S||Smith, M||Soares-Santos, M||Suchyta, E||Tarle, G||Walker, AR

publication date

  • May 2020