Simulations show SMBH feedback seeds IGM fields that match z=0 gamma-ray limits but fall short at z~3
Cosmological MHD simulations demonstrate that galactic feedback can magnetize the IGM to observed levels by z=0 but requires either modified high-z prescriptions or an additional primordial component to satisfy z~3 constraints. Dynamo amplification erases most differences in final halo field strength while preserving topology distinctions. The work highlights the need for joint constraints from Faraday rotation, gamma-ray cascades, and high-redshift observables.
Ramesh et al. ran 25 Mpc/h moving-mesh simulations injecting magnetic energy at supernova and supermassive-black-hole feedback events atop the IllustrisTNG model, then compared outcomes against uniform primordial-seed runs. Halo fields converge to similar strengths by z=0 via small-scale and halo dynamos regardless of seeding channel, yet SMBH injection yields systematically shorter coherence lengths. Feedback-driven runs accelerate dynamo onset and improve numerical convergence in low-mass halos. In the IGM, only the SMBH prescription satisfies present-day lower limits from gamma-ray cascade observations; both seeding families remain in tension at z~3, implying either stronger high-redshift feedback or a mixed primordial-plus-astrophysical origin.
Ramesh et al.: Increasing SMBH magnetic injection efficiency by 0.5 dex will bring simulated IGM fields above the z=3 gamma-ray lower limit in the next 25 Mpc/h rerun.
Sources (3)
- [1]Primary Source(https://arxiv.org/abs/2607.08812)
- [2]Supporting Source(https://arxiv.org/abs/2007.07956)
- [3]Supporting Source(https://ui.adsabs.harvard.edu/abs/2022MNRAS.514.2984P)