A compact symmetric radio source born at one-tenth the current age of the Universe

TL;DR

This paper reports the discovery and analysis of J1606+3124, a very high redshift compact symmetric radio source, providing insights into early AGN activity and galaxy evolution in the Universe's first billion years.

Contribution

It presents the identification and detailed VLBI analysis of J1606+3124 as the highest redshift CSO, offering new data on early galaxy and AGN development.

Findings

J1606+3124 is a young (~3600 years) compact symmetric object at redshift 4.56.

The source exhibits edge-brightening, peaked spectrum, and low jet speed, consistent with CSO characteristics.

Infrared data suggest a gas-rich environment that may influence jet growth.

Abstract

Studies of high redshift radio galaxies can shed light on the activity of active galactic nuclei (AGN) in massive elliptical galaxies, and on the assembly and evolution of galaxy clusters in the Universe. J1606+3124 has been tentatively identified as a radio galaxy at a redshift of 4.56, at an era of one-tenth of the current age of the Universe. Very long baseline interferometry (VLBI) images show a compact triple structure with a size of 68 parsecs. The radio properties of J1606+3124, including the edge-brightening morphology, peaked GHz radio spectrum, slow variability, and low jet speed, consistently indicate that it is a compact symmetric object (CSO). The radio source size and expansion rate of the hotspots suggest that J1606+3124 is a young (kinematic age of ~3600 years) radio source. Infrared observations reveal a gas- and dust-rich host galaxy environment, which may hinder the growth of the jet; however, the ultra-high jet power of J1606+3124 gives it an excellent chance to grow into a large-scale double-lobe radio galaxy. If its redshift and galaxy classification can be confirmed by further optical spectroscopic observations, J1606+3124 will be the highest redshift CSO galaxy known to date.