Models of the strongly lensed quasar DES J0408-5354
  We present gravitational lens models of the multiply imaged quasar DES
J0408-5354, recently discovered in the Dark Energy Survey (DES) footprint, with
the aim of interpreting its remarkable quad-like configuration. We first model
the DES single-epoch $grizY$ images as a superposition of a lens galaxy and
four point-like objects, obtaining spectral energy distributions (SEDs) and
relative positions for the objects. Three of the point sources (A,B,D) have
SEDs compatible with the discovery quasar spectra, while the faintest
point-like image (G2/C) shows significant reddening and a `grey' dimming of
$\approx0.8$mag. In order to understand the lens configuration, we fit
different models to the relative positions of A,B,D. Models with just a single
deflector predict a fourth image at the location of G2/C but considerably
brighter and bluer. The addition of a small satellite galaxy ($R_{\rm
E}\approx0.2$") in the lens plane near the position of G2/C suppresses the flux
of the fourth image and can explain both the reddening and grey dimming. All
models predict a main deflector with Einstein radius between $1.7"$ and $2.0",$
velocity dispersion $267-280$km/s and enclosed mass $\approx
6\times10^{11}M_{\odot},$ even though higher resolution imaging data are needed
to break residual degeneracies in model parameters. The longest time-delay
(B-A) is estimated as $\approx 85$ (resp. $\approx125$) days by models with
(resp. without) a perturber near G2/C. The configuration and predicted
time-delays of J0408-5354 make it an excellent target for follow-up aimed at
understanding the source quasar host galaxy and substructure in the lens, and
measuring cosmological parameters. We also discuss some lessons learnt from
J0408-5354 on lensed quasar finding strategies, due to its chromaticity and
morphology.
