AzTEC 1.1 mm images of 16 radio galaxies at 0.5<z<5.2 and a quasar at z=6.3

TL;DR

This study uses 1.1 mm observations to identify luminous star-forming galaxies associated with high-redshift radio galaxies and quasars, revealing their properties and potential as beacons for distant, dusty starbursts.

Contribution

It provides the first extensive millimetre imaging of high-z radio galaxies, linking their properties with star formation and mid-infrared characteristics, and highlights their role in finding luminous high-z galaxies.

Findings

Probable millimetre counterparts detected for 11 of 16 active galaxies.

Star formation rates range from <200 to ~1300 M/yr in detected sources.

Radio galaxy 1.1 mm flux density is anticorrelated with radio source size.

Abstract

We present 1.1 mm observations for a sample of 16 powerful radio galaxies at 0.5<z<5.2 and a radio quiet quasar at z=6.3, obtained using the AzTEC bolometer array mounted on the ASTE or the JCMT. This paper more than doubles the number of high-z radio galaxies imaged at millimetre/sub-millimetre wavelengths. We detect probable millimetre-wave counterparts for 11 of the active galaxies. The 6 active galaxies which do not have a probable millimetre counterpart in our images nevertheless have one or more likely associated millimetric source. Thus, we conclude that powerful (radio-loud) active galaxies at high-z are beacons for finding luminous millimetre/sub-millimetre galaxies at high-z. The flux densities of our AzTEC counterparts imply star formation rates ranging from <200 to ~1300 M./yr. In addition, we find that for the radio galaxoes the 1.1 mm flux density is anticorrelated with the largest angular size of the radio source. We also present new Spitzer imaging observations of several active galaxies in our sample. Combining these with archival data, we examine the mid-infrared colours of our sample. We find that radio galaxies for which we have detected a probable 1.1 mm counterpart have mid-infrared colours consistent with dusty starbursts, and are usually bluer than high-z Spitzer-selected active galaxies. In addition, we find arcs of 24 micron sources extending across ~200-500 kpc, apparently associated with three of the radio galaxies.