Interpreting MAD within multiple accretion regimes

TL;DR

This paper develops a model to interpret MAD accretion systems across different regimes and applies it to observational data, suggesting many radio-loud galaxies may be MAD systems even in radiatively inefficient states.

Contribution

It introduces a framework to understand MAD systems in multiple accretion regimes and tests it against observational data, expanding the applicability beyond radiatively efficient conditions.

Findings

Most radiatively inefficient radio-loud galaxies are consistent with MAD systems.

A significant fraction of the sample could be MAD systems across different regimes.

Future simulations are needed to verify the model's assumptions.

Abstract

General relativistic magnetohydrodynamic (GRMHD) simulations of accreting black holes in the radiatively inefficient regime show that systems with sufficient magnetic poloidal flux become magnetically arrested disc (MAD) systems, with a well-defined relationship between the magnetic flux and the mass accretion rate. Recently, Zamaninasab (2014) report that the jet magnetic flux and accretion disc luminosity are tightly correlated over 7 orders of magnitude for a sample of 76 radio-loud active galaxies, concluding that the data are explained by the MAD mode of accretion. Their analysis assumes radiatively efficient accretion, and their sample consists primarily of radiatively efficient sources, while GRMHD simulations of MAD thus far have been carried out in the radiatively inefficient regime. We propose a model to interpret MAD systems in the context of multiple accretion regimes, and apply it to the sample in Zamaninasab (2014), along with additional radiatively inefficient sources from archival data. We show that most of the radiatively inefficient radio-loud galaxies are consistent with being MAD systems. Assuming the MAD relationship found in radiatively inefficient simulations holds at other accretion regimes, a significant fraction of our sample can be candidates for MAD systems. Future GRMHD simulations have yet to verify the validity of this assumption.