PI: Adrianne Slyz

(co-PI Mahsa Sanati)

Despite the vast amount of energy released by active galactic nuclei (AGNs), their role in early galaxy formation and in regulating the growth of black holes (BHs) remains poorly understood. Motivated by new James Webb Space Telescope (JWST) observations of high redshift quasars residing in dwarf-mass galaxies, in dp016 we developed a cosmological zoom-in simulation suite to investigate the co-evolution of BHs and their host galaxies. This suite is designed to tackle one of the central challenges in this field: capturing the vast dynamical range from small-scale BH accretion to large-scale stellar and AGN-driven feedback. These simulations introduce several technical improvements that build upon previous numerical efforts to model early galaxy-AGN interplay: (i) comprehensive AGN feedback models capture both radio and quasar modes and include coupled radiative transfer, rarely accounted for at this resolution; (ii) high spatial resolution removes the need for artificial boosts to BH accretion or feedback, resolves the multiphase interstellar medium, and allows detailed tracking of ionizing radiation escape and AGN-driven outflows during uncapped super-Eddington episodes; (iii) the BH is not fixed to the galaxy centre, responding to gas inflows from the circumgalactic medium, while radiative feedback prevents cold clump formation and early stochastic displacements; (iv) the BH seed forms self-consistently in the first star-forming region. This naturally suppresses early star formation, enhances gas availability for accretion, and stabilizes BH dynamics by deepening the central potential within a nuclear star-forming region; (v) a detailed treatment of magneto-thermo-turbulent star formation and mechanical, radiative, and magnetic stellar feedback ensures realistic gas evolution and sustained BH growth.

Figure: (right) Gas density projection at redshift 8 highlighting AGN-driven high velocity outflows (in red) breaking out of the simulated dwarf galaxy. The white circle shows the inner portion of the virial radius, and the central black circle marks the BH. (middle) Density-weighted magnetic energy projection. White contours trace the magnetic field structure, showing its alignment with galactic-scale outflows that carry magnetic energy and shape both the host galaxy and its surroundings. (left) Inferred magnetic field orientation from FIR emission, capturing the turbulent and small-scale field close to the central BH.

We find our measurements in broad agreement with moderate luminosity quasars recently observed by JWST, producing overmassive BHs and high, though short-lived, Eddington fraction accretion rates (Sanati et al. 2025, MNRAS, 544, 4317). These results advocate for a scenario where AGN feedback allows for rapid BH growth during the reionization era, while driving winds that extend deep into the intergalactic medium, shaping host galaxies as well as more distant surroundings. These simulations form the baseline for the extended AGN models we are running on DiRAC’s Memory Intensive Service COSMA8 to include magnetic feedback and cosmic rays, which will enable us to probe the impact of even more comprehensive AGN feedback on BH growth and galaxy evolution in a fully cosmological context.