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Abstract:

Context. The properties and evolution of magnetic fields surrounding galaxies are observationally largely unconstrained. The detection and study of these magnetic fields is important to understand galaxy evolution since magnetic fields are tracers for dynamical processes in the circumgalactic medium (CGM) and can have a significant impact on the evolution of the CGM.
Aims. The Faraday rotation measure (RM) of the polarized light of background radio sources passing through the magnetized CGM of intervening galaxies can be used as a tracer for the strength and extent of magnetic fields around galaxies.
Methods. We used rotation measures observed by the MIGHTEE-POL (MeerKAT International GHz Tiered Extragalactic Exploration polarization) survey by MeerKAT in the XMM-LSS and COSMOS fields to investigate the RM around foreground star-forming galaxies. We used spectroscopic catalogs of star-forming and blue cloud galaxies to measure the RM of MIGHTEE-POL sources as a function of the impact parameter from the intervening galaxy. In addition, we examined the dependence of the RM on redshift. We then repeated this procedure using a deeper galaxy catalog with photometric redshifts.
Results. For the spectroscopic star-forming sample, we find a redshift-corrected |RM| excess of 5.6 ± 2.3 rad m−2 which corresponds to a 2.5σ significance around galaxies with a median redshift of z = 0.46 for impact parameters below 130 kpc only selecting the intervenor with the smallest impact parameter. Making use of a photometric galaxy catalog and taking into account all intervenors with Mg < −13.6 mag, the signal disappears. We find no indication for a correlation between redshift and RM, nor do we find a connection between the total number of intervenors to the total |RM|.
Conclusions. We have presented tentative evidence that the CGM of star-forming galaxies is permeated by coherent magnetic fields within the virial radius. We conclude that mostly bright, star-forming galaxies with impact parameters less than 130 kpc significantly contribute to the RM of the background radio source.

Abstract:

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 Mdyn ∼ 1011 M and a rotation-to-random motion ratio vrot/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