Discovery of two gravitationally lensed quasars in the Dark Energy Survey

Kavli Affiliate: Kevin Reil

| First 5 Authors: Adriano Agnello, Tommaso Treu, Fernanda Ostrovski, Paul L. Schechter, Elizabeth J. Buckley-Geer

| Summary:

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 $1.6times10^{11},M_{odot}.$ 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.

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