The power of relativistic jets is larger than the luminosity of their accretion disks

TL;DR

This study demonstrates that in blazars, the power of relativistic jets exceeds the luminosity of their accretion disks, indicating maximum magnetic field strength at the black hole horizon and supporting theoretical models of jet production.

Contribution

The paper provides the first clear observational evidence that jet power surpasses accretion disk luminosity in blazars, confirming predictions about magnetic field saturation near black holes.

Findings

Jet power exceeds accretion luminosity in blazars.

Correlation between gamma-ray jet power and broad emission line luminosity.

Magnetic field at the black hole horizon reaches maximum sustainable value.

Abstract

Theoretical models for the production of relativistic jets from active galactic nuclei predict that jet power arises from the spin and mass of the central black hole, as well as the magnetic field near the event horizon. The physical mechanism mechanism underlying the contribution from the magnetic field is the torque exerted on the rotating black hole by the field amplified by the accreting material. If the squared magnetic field is proportional to the accretion rate, then there will be a correlation between jet power and accretion luminosity. There is evidence for such a correlation, but inadequate knowledge of the accretion luminosity of the limited and inhomogeneous used samples prevented a firm conclusion. Here we report an analysis of archival observations of a sample of blazars (quasars whose jets point towards Earth) that overcomes previous limitations. We find a clear correlation between jet power as measured through the gamma-ray luminosity, and accretion luminosity as measured by the broad emission lines, with the jet power dominating over the disk luminosity, in agreement with numerical simulations. This implies that the magnetic field threading the black hole horizon reaches the maximum value sustainable by the accreting matter.