The nearby extreme accretion and feedback system PDS 456: finding a complex radio-emitting nucleus

TL;DR

This study uses VLBI observations to reveal a complex radio-emitting nucleus in the quasar PDS 456, showing a jet and extended emission likely caused by winds interacting with star-forming regions, highlighting extreme accretion feedback.

Contribution

First detailed VLBI imaging of PDS 456's nucleus, uncovering a complex radio structure associated with accretion-driven winds and feedback processes in a nearby quasar.

Findings

Detected a collimated jet and extended radio emission region.

The diffuse emission is about 360 pc in size and thrice as luminous as Arp 220.

Radio activity likely results from winds impacting star-forming regions.

Abstract

When a black hole accretes close to the Eddington limit, the astrophysical jet is often accompanied by radiatively driven, wide-aperture and mildly relativistic winds. Powerful winds can produce significant non-thermal radio emission via shocks. Among the nearby critical accretion quasars, PDS 456 has a very massive black hole (about one billion solar masses), shows a significant star-forming activity (about seventy solar masses per year) and hosts exceptionally energetic X-ray winds (power up to twenty per cent of the Eddington luminosity). To probe the radio activity in this extreme accretion and feedback system, we performed very-long-baseline interferometric (VLBI) observations of PDS 456 at 1.66 GHz with the European VLBI Network (EVN) and the enhanced Multi-Element Remotely Linked Interferometry Network (e-MERLIN). We find a rarely-seen complex radio-emitting nucleus consisting of a collimated jet and an extended non-thermal radio emission region. The diffuse emission region has a size of about 360 pc and a radio luminosity about three times higher than the nearby extreme starburst galaxy Arp 220. The powerful nuclear radio activity could result from either a relic jet with a peculiar geometry (nearly along the line of sight) or more likely from diffuse shocks formed naturally by the existing high-speed winds impacting on high-density star-forming regions.