Active Galactic Nuclei (AGN) in cosmological simulations generate explosive
feedback that regulates star formation in massive galaxies, modifying the gas
phase structure out to large distances. Here, we explore the direct effects
that AGN radiation has on gas heating and cooling within one high-resolution
z=3 dark matter halo as massive as a quasar host (Mh=1012.5M⊙), run without AGN feedback. We assume AGN radiation to
impact the circumgalactic medium (CGM) anisotropically, within a bi-cone of
angle α. We find that even a relatively weak AGN (black hole mass
M∙=108M⊙ with an Eddington ratio
λ=0.1) can significantly lower the fraction of halo gas that is
catastrophically cooling compared to the case of gas photoionized only by the
ultraviolet background (UVB). Varying M∙, λ and α,
we study their effects on observables. A 109M⊙ AGN with
λ=0.1 and α≊60o reproduces the average surface
brightness (SB) profiles of Lyα, HeII and CIV, and results in a covering
fraction of optically thick absorbers within observational estimates. The
simulated SBCIV profile is steeper than observed, indicating that not
enough metals are pushed beyond the very inner CGM. For this combination of
parameters, the CGM mass catastrophically cooling is reduced by half with
respect to the UVB-only case, with roughly same mass out of hydrostatic
equilibrium heating up and cooling down, hinting to the importance of
self-regulation around AGNs. This study showcases how CGM observations can
constrain not only the properties of the CGM itself, but also those of the AGN
engine.Comment: accepted for publication in MNRA