The jet-disc connection in AGN

TL;DR

This study investigates the relationship between accretion rates and jet power in active galactic nuclei, revealing a smooth transition at a critical accretion rate and emphasizing the connection between accretion regimes and jet properties.

Contribution

It demonstrates the link between accretion rate and jet power across different AGN types, including radio galaxies, and identifies the transition point between accretion regimes.

Findings

Correlation between broad line emission and jet luminosities in blazars.

Transition between radiatively efficient and inefficient accretion occurs at Ld/LEdd ~ 10^-2.

Below this threshold, ionizing luminosity drops significantly.

Abstract

We present our latest results on the connection between accretion rate and relativistic jet power in AGN, by using a large sample which includes mostly blazars, but contains also some radio--galaxies. The jet power can be traced by $\gamma$--ray luminosity in the case of blazars, and radio luminosity for both classes. The accretion disc luminosity is instead traced by the broad emission lines. Among blazars, we find a correlation between broad line emission and the $\gamma$--ray or radio luminosities, suggesting a direct tight connection between jet power and accretion rate. We confirm that the observational differences between blazar subclasses reflect differences in the accretion regime, but with blazars only we cannot properly access the low--accretion regime. By introducing radio--galaxies, we succeed in observing the fingerprint of the transition between radiatively efficient and inefficient accretion discs in the jetted AGN family. The transition occurs at the standard critical value $L_{\rm d}/L_{\rm Edd}\sim10^{-2}$ and it appears smooth. Below this value, the ionizing luminosity emitted by the accretion structure drops significantly.