2023A&A...679A..89P

Context. LBQS 0302-0019 is a blue quasar (QSO) at z ∼ 3.3 that hosts powerful outflows and resides in a complex environment consisting of an obscured active galactic nucleus (AGN) candidate and multiple companions, all within 30 kpc in projection.
Aims. We aim to characterise this complex system using JWST NIRSpec Integral Field Spectrograph (IFS) observations obtained as part of the NIRSpec IFS GTO programme “Galaxy Assembly with NIRSpec IFS” (GA-NIFS); these data cover the QSO rest-frame optical emission lines with a spatial resolution of ∼0.1″ and a sampling of 0.05″ (∼380 pc) over a contiguous sky area of ∼3″ × 3″ (23 × 23 kpc²).
Methods. We developed a procedure to correct for the spurious oscillations (or “wiggles”) in NIRSpec single-spaxel spectra caused by the spatial under-sampling of the point spread function. We performed a QSO-host decomposition with the QDEBLEND3D tools. We used multi-component kinematic decomposition of the optical emission line profiles to infer the physical properties of the emitting gas in the QSO environment.
Results. The QSO-host decomposition allows us to identify both a low- and a high-velocity component. The former possibly traces a warm rotating disk with a dynamical mass M_dyn ∼ 10¹¹ M_⊙ and a rotation-to-random motion ratio v_rot/σ₀ ∼ 2. The other kinematic component traces a spatially unresolved ionised outflow with a velocity of ∼1000 km s^–1 and an outflow mass rate of ∼10⁴ M_⊙ yr^–1. We clearly detect eight companion objects close to LBQS 0302-0019. For two of them, we detect a regular velocity field that likely traces rotating gas, and we infer individual dynamical masses of ≈10¹⁰ M_⊙. Another companion shows evidence of gravitational interaction with the QSO host. Optical line ratios confirm the presence of a second, obscured AGN ∼20 kpc from the primary QSO; the dual AGN dominates the ionisation state of the gas in the entire NIRSpec field of view.
Conclusions. This work has unveiled in unprecedented detail the complex environment of LBQS 0302-0019, which includes its host galaxy, a close obscured AGN, and nine interacting companions (five of which were previously unknown), all within 30 kpc of the QSO. Our results support a scenario where mergers can trigger dual AGN and can be important drivers of rapid early supermassive black hole growth.