Clusters' far-reaching influence on narrow-angle tail radio galaxies

TL;DR

This study analyzes 208 narrow-angle tail radio galaxies in clusters, revealing their distribution and orientation patterns suggest they are on radial orbits and influenced by intracluster medium interactions far beyond the cluster core.

Contribution

It provides new insights into the spatial distribution and orbital dynamics of NATs, highlighting their influence on and interaction with the intracluster medium at large radii.

Findings

NATs are predominantly on radial inbound orbits.

NATs show jet bending towards cluster cores even beyond the virial radius.

Significant deceleration of inflowing medium occurs at large radii, affecting NAT morphology.

Abstract

In order to study the ram-pressure interaction between radio galaxies and the intracluster medium, we analyse a sample of 208 highly-bent narrow-angle tail radio sources (NATs) in clusters, detected by the LOFAR Two-metre Sky Survey. For NATs within $7\,R_{500}$ of the cluster centre, we find that their tails are distributed anisotropically with a strong tendency to be bent radially away from the cluster, which suggests that they are predominantly on radially inbound orbits. Within $0.5\,R_{500}$, we also observe an excess of NATs with their jets bent towards the cluster core, indicating that these outbound sources fade away soon after passing pericentre. For the subset of NATs with spectroscopic redshifts, we find the radial bias in the jet angles exists even out to $10\,R_{500}$, far beyond the virial radius. The presence of NATs at such large radii implies that significant deceleration of the accompanying inflowing intergalactic medium must be occurring there to create the ram pressure that bends the jets, and potentially even triggers the radio source.