A cosmic dance at z~3: Detecting the host galaxies of the dual AGN
  system LBQS0302-0019 and Jil with HAWK-I+GRAAL
  We recently discovered that the luminous radio-quiet QSO LBQS0302-0019 at
z=3.286 is likely accompanied by an obscured AGN at 20kpc projected distance,
which we dubbed Jil. It represents the tightest candidate obscured/unobscured
dual AGN system at z>3. To verify the dual AGN scenario we obtained deep $K_s$
band (rest-frame $V$ band) imaging with the VLT/HAWK-I+GRAAL instrument at 0.4"
resolution during science verification in January 2018. Indeed, we detect the
individual host galaxies of the QSO and Jil with estimated stellar masses of
$\log(M_\star/M_{\odot})=11.4\pm0.5$ and $\log(M_\star/M_{\odot})=10.9\pm0.5$,
respectively. Near-IR spectra obtained with VLT-KMOS reveal a clear [OIII]
$\lambda$5007 line detection at the location of Jil which does not contribute
significantly to the $K_s$ band flux. Both observations therefore corroborate
the dual AGN scenario. A comparison to Illustris cosmological simulations
suggests a parent halo mass of $\log(M_\mathrm{halo}/M_{\odot})=13.2\pm0.5$ for
this interacting galaxy system, corresponding to a very massive dark matter
halo at that epoch.
