Radio-loud high-redshift protogalaxy candidates in Bootes

TL;DR

This study identifies and characterizes four high-redshift radio galaxy candidates in Bootes using near-infrared imaging, revealing their potential early formation stages and high redshifts.

Contribution

First near-infrared imaging of optically faint, radio-loud high-redshift galaxy candidates in Bootes, providing insights into their redshifts and morphologies.

Findings

Three objects likely at z > 3 with high radio luminosities

Two objects show diffuse morphologies indicating ongoing formation

One object possibly at higher redshift than photometric estimates

Abstract

We used the Near Infrared Camera on Keck I to obtain Ks-band images of four candidate high-redshift radio galaxies selected using optical and radio data in the NOAO Deep Wide-Field Survey in Bootes. Our targets have 1.4 GHz radio flux densities greater than 1 mJy, but are undetected in the optical to fainter than 24 Vega mag. Spectral energy distribution fitting suggests that three of these objects are at z > 3, with radio luminosities near the FR-I / FR-II break. The other has photometric redshift 1.2, but may in fact be at higher redshift. Two of the four objects exhibit diffuse morphologies in Ks -band, suggesting that they are still in the process of forming.