Radio emission from dust-obscured galaxies

TL;DR

This study investigates the radio properties of dust-obscured galaxies (DOGs) to understand their evolutionary stage and black hole activity, revealing that a small fraction are radio-bright, mainly 'power-law' DOGs, with weak emission in others.

Contribution

It provides the first large-scale analysis of radio emission in DOGs, distinguishing between different spectral types and their radio detectability, highlighting the prevalence of weak radio signals.

Findings

Only about 2% of DOGs are radio-detected in FIRST survey.

Radio-detected DOGs are mostly 'power-law' type.

Weak radio emission is present in 'power-law' DOGs, while 'bump' DOGs show marginal detection.

Abstract

The coevolution of galaxies and their central supermassive black holes is a subject of intense research. A class of objects, the dust-obscured galaxies (DOGs) are particularly interesting in this respect as they are thought to represent a short evolutionary phase when violent star formation activity in the host galaxy may coexist with matter accretion onto the black hole powering the active nucleus. Here we investigate different types of DOGs classified by their mid-infrared spectral energy distributions to reveal whether they can be distinguished by their arcsec-scale radio properties. Radio emission is unaffected by dust obscuration and may originate from both star formation and an active nucleus. We analyse a large sample of 661 DOGs complied from the literature and find that only a small fraction of them ($\sim 2$ per cent) are detected with flux densities exceeding $\sim 1$ mJy in the Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) survey. These radio-detected objects are almost exclusively `power-law' DOGs. Stacking analysis of the FIRST image cutouts centred on the positions of individually radio-undetected sources suggests that weak radio emission is present in `power-law' DOGs. On the other hand, radio emission from `bump' DOGs is only marginally detected in the median-stacked FIRST image.