Resolved Dust Emission in a Quasar at z=3.65

TL;DR

This study reports detailed submillimetre observations of a high-redshift quasar with extraordinary IR luminosity, revealing extended emission likely due to a galaxy merger or jet activity, providing insights into early galaxy evolution.

Contribution

First high-resolution submm imaging of a z=3.65 quasar showing extended emission and complex morphology, suggesting early-stage galaxy merger or jet-induced star formation.

Findings

Extended submm emission on 10-35 kpc scales.

Offset of ~10 kpc between submm and optical emission.

Likely early-stage galaxy merger or jet activity.

Abstract

We present submillimetre observations of the z=3.653 quasar SDSS160705+533558 together with data in the optical and infrared. The object is unusually bright in the far-IR and submm with an IR luminosity of ~10^14 L_sun. We ascribe this luminosity to a combination of AGN and starburst emission, with the starburst forming stars at a rate of a few thousand solar masses per year. Submillimetre Array (SMA) imaging observations with a resolution ~1" show that the submm (850 micron) emission is extended on scales of 10--35kpc and is offset from the optical position by ~10 kpc. This morphology is dissimilar to that found in submm galaxies, which are generally un- or marginally resolved on arcsecond scales, or submm-luminous AGN where the AGN lies at the peak of the submm or molecular emission. The simplest explanation is that the object is in the early stages of a merger between a gas rich galaxy, which hosts the starburst, and a gas-poor AGN-host galaxy, which is responsible for the quasar emission. It is also possible that jet induced star formation might contribute to the unusual morphology.