We recently discovered that the luminous radio-quiet QSO LBQS 0302 - 0019 at z = 3.286 is likely accompanied by an obscured AGN at 20 kpc 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 \aas@@fstack { \prime \prime } 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 \pm 0.5 and \log ( M _ { \star } / M _ { \odot } ) = 10.9 \pm 0.5 , respectively .
Near-IR spectra obtained with VLT-KMOS reveal a clear [ O iii ] \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 \pm 0.5 for this interacting galaxy system , corresponding to a very massive dark matter halo at that epoch .