DES meets Gaia: discovery of strongly lensed quasars from a multiplet search


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We report the discovery, spectroscopic confirmation and first lens models of the first two, strongly lensed quasars from a combined search in WISE and Gaia over the DES footprint. The four-image lensWGD2038-4008 (r.a.=20:38:02.65, dec.=-40:08:14.64) has source- and lens-redshifts $z_{s}=0.777 pm 0.001$ and $z_l = 0.230 pm 0.002$ respectively. Its deflector has effective radius $R_{rm eff} approx 3.4^{primeprime}$, stellar mass $log(M_{star}/M_{odot}) = 11.64^{+0.20}_{-0.43}$, and shows extended isophotal shape variation. Simple lens models yield Einstein radii $R_{rm E}=(1.30pm0.04)^{primeprime},$ axis ratio $q=0.75pm0.1$ (compatible with that of the starlight) and considerable shear-ellipticity degeneracies. The two-image lensWGD2021-4115 (r.a.=20:21:39.45, dec.=--41:15:57.11) has $z_{s}=1.390pm0.001$ and $z_l = 0.335 pm 0.002$, and Einstein radius $R_{rm E} = (1.1pm0.1)^{primeprime},$ but higher-resolution imaging is needed to accurately separate the deflector and faint quasar image. We also show high-rank candidate doubles selected this way, some of which have been independently identified with different techniques, and discuss a DES+WISE quasar multiplet selection.

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