The discovery of a typical radio galaxy at z = 4.88

TL;DR

This paper reports the discovery of a typical radio galaxy at redshift 4.88 using a new technique that does not depend on traditional radio property pre-selection, demonstrating the potential for finding distant radio sources.

Contribution

The paper introduces a novel method for discovering high-redshift radio galaxies without relying on pre-selected radio properties, expanding the search for distant radio sources.

Findings

Discovered a z=4.88 radio galaxy with typical luminosity.

Host galaxy mass comparable to lower redshift counterparts.

Demonstrated the effectiveness of the new survey technique.

Abstract

In this letter we report the discovery of a z=4.88 radio galaxy discovered with a new technique which does not rely on pre-selection of a sample based on radio properties such as steep-spectral index or small angular size. This radio galaxy was discovered in the Elais-N2 field and has a spectral index of alpha = 0.75, i.e. not ultra-steep spectrum. It also has a luminosity consistent with being drawn from the break of the radio luminosity function and can therefore be considered as a typical radio galaxy. Using the Spitzer-SWIRE data over this field we find that the host galaxy is consistent with being similarly massive to the lower redshift powerful radio galaxies (~1-3L*). We note however, that at z=4.88 the H-alpha line is redshifted into the IRAC 3.6micron filter and some of the flux in this band may be due to this rather than stellar continuum emission. The discovery of such a distant radio source from our initial spectroscopic observations demonstrate the promise of our survey for finding the most distant radio sources.