A path to radio-loudness through gas-poor galaxy mergers and the role of retrograde accretion

TL;DR

This paper proposes that retrograde accretion onto spinning black holes, often resulting from gas-poor galaxy mergers, can explain the emergence of radio-loud active galactic nuclei and their connection to galaxy morphology.

Contribution

It introduces a new pathway linking galaxy mergers, retrograde accretion, and radio-loudness in AGN, unifying observed phenomena with black hole accretion dynamics.

Findings

Retrograde accretion is associated with gas-poor galaxy mergers.

Retrograde accretion may trigger powerful jets in radio-loud AGN.

This mechanism could explain the galaxy morphology and radio-loudness dichotomy.

Abstract

In this proceeding we explore a pathway to radio-loudness under the hypothesis that retrograde accretion onto giant spinning black holes leads to the launch of powerful jets, as seen in radio loud QSOs and recently in LAT/Fermi and BAT/Swift Blazars. Counter-rotation of the accretion disc relative to the BH spin is here associated to gas-poor galaxy mergers progenitors of giant (missing-light) ellipticals. The occurrence of retrograde accretion enters as unifying element that may account for the radio-loudness/galaxy morphology dichotomy observed in AGN.