Abstract
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 1 billion solar masses), shows a significant star-forming activity (about 70 solar masses per year), and hosts exceptionally energetic X-ray winds (power up to 20 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 and the enhanced Multi-Element Remotely Linked Interferometry Network. 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 that of the nearby extreme starburst galaxy Arp 220. The powerful nuclear radio activity could result either from 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.
Highlights
Accreting supermassive black holes (SMBHs) can provide mechanical feedback on their host galaxies via launching jets and winds
We corrected the ionospheric dispersive delays according to the maps of total electron content provided by global positioning system satellite observations, removed phase errors due to the antenna parallactic angle variations, and aligned the phases across the subbands via running fringe fitting with a 2-min scan of the National Radio Astronomy Observatory (NRAO) 530 data
Compared to the previous star formation rate (SFR) estimate based on spectral energy distribution (SED) fitting by Yun et al (2004), we add two Wide-field Infrared Survey Explorer (WISE) bands at 12 and 22 μm, two Herschel PACS (Photodetector Array Camera and Spectrometer) bands at 70 and 160 μm, and three SPIRE (Spectral and Photometric Imaging REceiver) bands at 250, 350, and 500 μm
Summary
Accreting supermassive black holes (SMBHs) can provide mechanical feedback on their host galaxies via launching jets and winds. Lamastra et al 2017), and quench star formation (e.g. Kormendy & Ho 2013; Fiore et al 2017) Observing this complex nuclear radio activity with the very long baseline interferometric (VLBI) imaging technique can provide information to constrain physical properties in the extreme accreting environment and help understand feedback with the host galaxy. As a critical accretion system, PDS 456 is of great interest for probing powerful multiphase winds and outflows It hosts a quasispherical mildly relativistic ( 0.3c) X-ray wind with a very high kinetic energy of ∼0.2LEdd (Nardini et al 2015).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
