Radio emission from dust-obscured galaxies

Krisztina É Gabányi,Sándor Frey,Krisztina Perger

doi:10.1093/mnras/stab1923

Abstract

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 on to 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 (∼2 per cent) are detected with flux densities exceeding ∼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.

Highlights

Enhanced star formation and activity of the central supermassive black hole in galaxies as an active galactic nucleus (AGN) are both relatively short phases in the lifetime of a galaxy
If an extragalactic radio source at z 0.1 can be detected at mas-scale resolution with very long baseline radio interferometric (VLBI) technique, the radio emission has to originate from an AGN (Middelberg et al 2013)
We investigated the arcsec-scale radio emission of different dust-obscured galaxies (DOGs) samples using the FIRST survey catalogue

Summary

INTRODUCTION

Enhanced star formation and activity of the central supermassive black hole in galaxies as an active galactic nucleus (AGN) are both relatively short phases in the lifetime of a galaxy. The AGN contribution is more established in an extreme subsample of DOGs, the so-called hot DOG sources They were classified in a sample of luminous infrared galaxies detected by the Wide-field Infrared Survey Explorer space telescope (WISE, Wright et al 2010), and found to fulfil the DOG criteria. B12 studied a subsample of DOGs detected by Dey et al (2008) They focused on objects with spectroscopic redshifts above 1.4 and found tentative evidence supporting the evolutionary scenario where SMGs evolve first into B DOGs and into PL DOGs. Noboriguchi et al (2019) (hereafter N19) created a sample of 571 infrared-bright DOGs using optical and infrared data obtained with the Subaru Hyper Suprime-Cam (HSC; Aihara et al 2018) survey, the VISTA Kilo-degree Infrared Galaxy survey (VIKING DR2; Edge et al 2013), and the Wide-field Infrared Survey Explorer all-sky survey (AllWISE; Cutri & et al 2014).

SAMPLE SELECTION AND DATA

STACKING ANALYSIS

DETECTED SOURCES

Findings

DISCUSSION

CONCLUSIONS