XMAGNET: kinetic, thermal, and magnetic AGN feedback in massive galaxies at halo masses ∼1013.5 M⊙

ABSTRACT The interplay between radiative cooling of the circumgalactic medium (CGM) and feedback heating governs the evolution of the universe’s most massive galaxies. This paper presents simulations of feedback processes in massive galaxies showing how kinetic, thermal, and magnetic active galactic nuclei (AGNs) feedback interacts with the CGM under different environmental conditions. We find that in massive galaxies with shallower central gravitational potential and higher CGM pressure (multiphase galaxy; MPG) pure kinetic AGN feedback is most efficient in preventing CGM cooling from becoming catastrophic while maintaining the CGM entropy within the observed range. For the same galaxy, partitioning AGN energy injection into kinetic (75 per cent) and thermal (25 per cent) energy results in an entropy bump within r 15 kpc, while also having a larger amount of cold gas extending out to r 80 kpc. A magnetohydrodynamic (MHD) MPG run with seed magnetic field in the CGM (1 G) and partial magnetized AGN feedback (1 per cent of total AGN power) also shows a higher entropy (within r 15 kpc) and cold gas mass, albeit the cold gas remains constrained within r 30 kpc. For a similarly massive galaxy with deeper potential well and low CGM pressure (single-phase galaxy; SPG) our simulations show that for both hydro and MHD runs with partial thermal AGN energy, the feedback mechanism remains tightly self-regulating with centrally concentrated cooling (within r 1 kpc). Our simulations of a similar mass galaxy with a deeper potential well and higher CGM pressure (SPG-Cool) show that our AGN feedback mechanism cannot get rid of the high CGM density and pressure and its long-term evolution is similar to the MPG.