A magnified view of circumnuclear star formation and feedback around an AGN at z=2.6

TL;DR

This study uses ALMA observations to resolve a star-forming molecular ring around a z=2.6 AGN, revealing complex gas dynamics and limited feedback impact on star formation over tens of millions of years.

Contribution

First detailed ALMA imaging of circumnuclear star formation and feedback processes around a high-redshift AGN at 360 pc resolution.

Findings

Resolved a 2.5 kpc star-forming molecular ring.

Detected high-velocity dense molecular gas near the AGN.

Feedback effects are minimal on star formation within the ring.

Abstract

We present Atacama Large Millimeter/submillimeter Array observations of a radio-loud and millimeter-bright galaxy at z=2.6. Gravitational lensing by a foreground galaxy at z~0.2 provides access to physical scales of approximately 360 pc, and we resolve a 2.5 kpc-radius ring of star-forming molecular gas, traced by atomic carbon CI(1-0) and carbon monoxide CO(4-3). We also detect emission from the cyanide radical, CN(4-3). With a velocity width of 680 km/s, this traces dense molecular gas travelling at velocities nearly a factor of two larger than the rotation speed of the molecular ring. While this could indicate the presence of a dynamical and photochemical interaction between the active galactic nucleus and molecular interstellar medium on scales of a few 100 pc, on-going feedback is unlikely to have a significant impact on the assembly of stellar mass in the molecular ring, given the ~10s Myr depletion timescale due to star formation.