Three-dimensional Global Relativistic Radiation Magnetohydrodynamics of Magnetically Arrested Disk Accretion Flows in AGNs

Abstract

We perform three-dimensional radiation-relativistic magnetohydrodynamic (3D Rad-RMHD) simulations of accretion flows around spinning active galactic nuclei (AGNs). Our study focuses on the magnetically arrested disk (MAD) state, adopting a single-temperature model that includes bremsstrahlung opacity as the sole radiation process while varying the black hole spin from non-spinning to rapidly spinning cases. We find that the MAD state persists across all spin values, as demonstrated by the normalized magnetic flux at the horizon and the physically motivated spatially averaged plasma beta. The overall flow dynamics remain qualitatively similar for all spin models in 3D flow, suggesting that black hole spin has minimal influence on the accretion dynamics. In addition, we conduct post-processing using a two-temperature model to calculate the luminosities from synchrotron and bremsstrahlung radiation. We find that the total radiation luminosity is significantly higher than the luminosities from synchrotron and bremsstrahlung. This finding highlights the influence of radiation on the dynamics of the accretion flow. Our analysis shows that the electron temperature is significantly high in the jet region, regardless of spin. We further find that the temporal evolution of both radiative and synchrotron luminosities exhibits qualitatively similar behavior across all spin values. Finally, our results indicate that black hole spin has minimal impact on the spectral energy distribution (SED) in MAD state accretion flows.

Figures (12)

• Figure 1: The distribution of density of the initial equilibrium torus $(a)$ for 2D slice in ($r-z$) plane for 3D model, and $(b)$ volume rendering plot at $t = 0~t_g$. The gray lines illustrate the magnetic field lines. Here, we fix spin of the black hole as $a_k = 0.98$.
• Figure 2: Comparison of temporal evolution of $(a)$: mass accretion rate ($\dot{M}_{\rm acc}$) in Eddington units ($\dot{M}_{\rm Edd}$), $(b)$: normalized magnetic flux ($\dot{\phi}_{\rm acc}$) accumulated at the black hole horizon and ($c$): spatial average plasma beta ($\beta_{\rm ave}$) with the simulation time for different black hole spin. Here, we consider the spin values as $a_k = 0.0, 0.20, 0.50, 0.80$, and $0.98$. See the text for details.
• Figure 3: Comparison of azimuthal and time averaged density ($\rho$), temperature ($T$), magnetization parameter ($\sigma_{\rm M}$) and Lorentz factor ($\Gamma$) in the ($r-z$) plane, respectively. Here, we fix the black hole spin as $a_k = 0.0, 0.20, 0.50, 0.80, 0.98$ and the time average between $t = 5000 t_g$ to $6000 t_g$. See the text for details.
• Figure 4: The distribution of azimuthal and time averaged of radiation energy density ($E_{\rm rad}$) is presented in the ($r-z$) plane using cylindrical coordinates in the upper panel and in the ($x-y$) equatorial plane using cartesian coordinates in the lower panel. We have fixed the black hole spin at values of $a_k = 0.0, 0.20, 0.50, 0.80,$ and $0.98$, with the time average between $t = 5000 t_g$ to $6000 t_g$. See the text for details.
• Figure 5: Radial profiles of vertically, azimuthally and density-weighted density $<\rho>$, temperature $<T>$, magnetic field $<|B|>$, plasma beta parameter $<\beta>$, radiation energy density $<E_{\rm rad}>$ and disk scale height $<h/r>$, respectively. The time average is taken from $t = 5000 t_g$ to $6000 t_g$.