Confirming a Population of Hot-Dust Dominated, Star Forming Ultraluminous Galaxies at High-Redshift

TL;DR

This study confirms the existence of high-redshift, hot-dust ULIRGs that are missed by submillimetre surveys, highlighting their properties and implications for future infrared observations.

Contribution

It provides the first direct confirmation of hot, dusty ULIRGs at high redshift that are not detected in submillimetre surveys, expanding understanding of galaxy populations.

Findings

Identified 8 z>1 ULIRGs with hotter dust temperatures than SMGs.

Confirmed star formation as the source of radio emission via high-resolution radio maps.

Highlighted the importance of infrared surveys like Herschel and SCUBA2 for detecting such galaxies.

Abstract

We identify eight z>1 radio sources undetected at 850um but robustly detected at 70um, confirming that they represent ultraluminous infrared galaxies (ULIRGs) with hotter dust temperatures (T_dust=52+-10 K) than Submillimetre Galaxies (SMGs) at similar luminosities and redshifts. These galaxies share many properties with SMGs: ultra-violet (UV) spectra consistent with starbursts, high stellar masses and radio luminosities. We can attribute their radio emission to star formation since high-resolution MERLIN radio maps show extended emission regions (with half light radii of 2-3kpc), which are unlikely to be generated by AGN activity. These observations provide the first direct confirmation of hot, dusty ULIRGs which are missed by current submillimetre surveys. They have significant implications for future observations from the Herschel Space Observatory and SCUBA2, which will select high redshift luminous galaxies with less selection biases.