VDES J2325-5229 a z=2.7 gravitationally lensed quasar discovered using
  morphology independent supervised machine learning
  We present the discovery and preliminary characterization of a
gravitationally lensed quasar with a source redshift $z_{s}=2.74$ and image
separation of $2.9"$ lensed by a foreground $z_{l}=0.40$ elliptical galaxy.
Since the images of gravitationally lensed quasars are the superposition of
multiple point sources and a foreground lensing galaxy, we have developed a
morphology independent multi-wavelength approach to the photometric selection
of lensed quasar candidates based on Gaussian Mixture Models (GMM) supervised
machine learning. Using this technique and $gi$ multicolour photometric
observations from the Dark Energy Survey (DES), near IR $JK$ photometry from
the VISTA Hemisphere Survey (VHS) and WISE mid IR photometry, we have
identified a candidate system with two catalogue components with $i_{AB}=18.61$
and $i_{AB}=20.44$ comprised of an elliptical galaxy and two blue point
sources. Spectroscopic follow-up with NTT and the use of an archival AAT
spectrum show that the point sources can be identified as a lensed quasar with
an emission line redshift of $z=2.739\pm0.003$ and a foreground early type
galaxy with $z=0.400\pm0.002$. We model the system as a single isothermal
ellipsoid and find the Einstein radius $\theta_E \sim 1.47"$, enclosed mass
$M_{enc} \sim 4 \times 10^{11}$M$_{\odot}$ and a time delay of $\sim$52 days.
The relatively wide separation, month scale time delay duration and high
redshift make this an ideal system for constraining the expansion rate beyond a
redshift of 1.
