A unified framework for X-shaped radio galaxies

TL;DR

This paper introduces a new unified model for X-shaped radio galaxies, linking their features to cold gas accretion onto Schwarzschild black holes, explaining their unique properties and environmental preferences.

Contribution

It presents a novel framework that redefines the understanding of X-shaped radio galaxies as transition objects influenced by accretion states and black hole spin.

Findings

X-shaped radio galaxies have smaller black hole masses.

They prefer isolated environments over clusters.

They are absent among the most powerful radio quasars.

Abstract

We propose a radically different picture for X-shaped radio galaxies compared to existing models as transition objects between cold mode accreting low spinning retrograde black holes and low spinning prograde black holes. The model explains their smaller average black hole masses, their general aversion for cluster compared to isolated environments, the negligible difference in spectral index between primary and secondary jets despite a time difference in their formation, their absence among the most powerful radio quasars and radio galaxies, and their connection to the elusive FRI quasar class, among others. The key to their formation is cold gas accretion onto Schwarzschild black holes.