The XXL Survey: XLIII. The quasar radio loudness dichotomy exposed via radio luminosity functions obtained by combining results from COSMOS and XXL-S X-ray selected quasars

Abstract

We studied a sample of 274 radio and X-ray selected quasars (XQSOs) detected in the COSMOS and XXL-S radio surveys at 3 GHz and 2.1 GHz, respectively. This sample was identified by adopting a conservative threshold in X-ray luminosity, Lx [2-10\ keV] >= 10^44 erg/s, selecting only the most powerful quasars. Using available multiwavelength data, we examined various criteria for the selection of radio-loud (RL) and radio-quiet (RQ) XQSOs, finding that the number of RL/RQ XQSOs changes significantly depending on the chosen criterion. This discrepancy arises due to the different criteria tracing different physical processes and due to our sample being selected from flux-limited radio and X-ray surveys. Another approach to study the origin of radio emission in XQSOs is via their radio luminosity function (RLF). We constructed the XQSO 1.4 GHz radio luminosity functions (RLFs) in six redshift bins at 0.5 <= z <= 3.7. The lower-1.4 GHz luminosity end shows a higher normalization than expected only from AGN contribution in all studied redshift bins. The found "bump" is mostly dominated by emission due to star-forming (SF) processes within the XQSO host galaxies. As expected, AGN-related radio emission dominates at the higher-luminosity end of RLF. The evolution of XQSO RLF was studied via combination of analytic forms from the literature to constrain the lower-luminosity "bump" and the higher-luminosity AGN part of the RLF. We defined two 1.4 GHz luminosity thresholds, L_th,SF and L_th,AGN, below and above which more than 80% of sources contributing to the RLF are dominated by SF and AGN-related activity, respectively. These thresholds evolve with redshift, most likely due to the strong evolution of SFRs of the XQSO host galaxies.

arXiv comment14 pages, 11 figures

References in corpus (50)

• The Global Schmidt Law in Star Forming Galaxies
• 3D-HST+CANDELS: The Evolution of the Galaxy Size-Mass Distribution since $z=3$
• The COSMOS2015 Catalog: Exploring the 1<z<6 Universe with half a million galaxies
• The Sloan Digital Sky Survey Quasar Catalog V. Seventh Data Release
• Radio Properties of Infrared Selected Galaxies in the IRAS 2 Jy Sample
• The Star-formation Mass Sequence out to z=2.5
• Active Galactic Nuclei: what's in a name?
• Optical and Radio Properties of Extragalactic Sources Observed by the FIRST and SDSS Surveys
• The Chandra COSMOS Legacy survey: overview and point source catalog
• The Expanded Very Large Array -- a New Telescope for New Science
• The VLA-COSMOS 3 GHz Large Project: Continuum data and source catalog release
• Chandra Snapshot Observations of Low-Luminosity AGNs with a Compact Radio Source
• Radio sources in the 6dFGS: Local luminosity functions at 1.4 GHz for star-forming galaxies and radio-loud AGN
• The Chandra COSMOS Legacy survey: optical/IR identifications
• The VLA-COSMOS Survey: II. Source Catalog of the Large Project
• The Mean Star Formation Rate of X-ray selected Active Galaxies and its Evolution from z=2.5: Results from PEP-Herschel
• The XXL Survey: I. Scientific motivations - XMM-Newton observing plan - Follow-up observations and simulation programme
• Radio sources in the 2dF Galaxy Redshift Survey - II. Local radio luminosity functions for AGN and star-forming galaxies at 1.4 GHz
• The Chandra COSMOS Survey: III. Optical and Infrared Identification of X-ray Point Sources
• The VLA-COSMOS Survey. IV. Deep Data and Joint Catalog
• On the origin of radio emission in radio quiet quasars
• Signals from the Noise: Image Stacking for Quasars in the FIRST Survey
• VLA-COSMOS 3GHz Large Project: The infrared-radio correlation of star-forming galaxies and AGN to $z\lesssim 6$
• The VLA-COSMOS 3 GHz Large Project: Multiwavelength counterparts and the composition of the faint radio population
• A remarkably flat relationship between the average star formation rate and AGN luminosity for distant X-ray AGN
• The VLA-COSMOS 3~GHz Large Project: AGN and host-galaxy properties out to z$\lesssim$6
• The VLA-COSMOS 3 GHz Large Project: The cosmic star formation history since z~5
• The VLA-VIRMOS Deep Field I. Radio observations probing the microJy source population
• The VLA-COSMOS 3~GHz Large Project: Cosmic evolution of radio AGN and implications for radio-mode feedback since z~5
• AGN and Starburst Radio Emission from Optically Selected QSOs
• The Mean Star-Forming Properties of QSO Host Galaxies
• The Two-Component Radio Luminosity Function of QSOs: Star Formation and AGN
• Is there a Dichotomy in the Radio Loudness Distribution of Quasars?
• Galaxy Evolution in the Radio Band: The Role of Starforming Galaxies and Active Galactic Nuclei
• The mean star formation rates of unobscured QSOs: searching for evidence of suppressed or enhanced star formation
• AGN vs. host galaxy properties in the COSMOS field
• A comparison of the optical properties of radio-loud and radio-quiet quasars
• GAMA/WiggleZ: The 1.4GHz radio luminosity functions of high- and low-excitation radio galaxies and their redshift evolution to z=0.75
• Disclosing the Radio Loudness Distribution Dichotomy in Quasars: An Unbiased Monte Carlo Approach Applied to the SDSS-FIRST Quasar Sample
• Radio-Quiet Quasars in the VIDEO Survey: Evidence for AGN-powered radio emission at S_1.4GHz < 1 mJy
• Multi-wavelength properties of Type 1 and Type 2 AGN Host Galaxies in the Chandra-COSMOS Legacy Survey
• Evidence that the AGN dominates the radio emission in z ~ 1 radio-quiet quasars
• The temperature dependence of the far-infrared-radio correlation in the Herschel-ATLAS
• Type 2 AGN host galaxies in the Chandra-COSMOS Legacy Survey: No Evidence of AGN-driven Quenching
• The VLA-COSMOS 3 GHz Large Project: Star formation properties and radio luminosity functions of AGN with moderate-to-high radiative luminosities out to $z\sim 6$
• Constraints on submicrojansky radio number counts based on evolving VLA-COSMOS luminosity functions
• The XXL Survey XVIII. ATCA 2.1 GHz radio source catalogue and source counts for the XXL-South field
• The XXL Survey: XXXI. Classification and host galaxy properties of 2.1 GHz ATCA XXL-S radio sources
• The XXL Survey : XXVI. Optical and near-infrared identifications of the ATCA 2.1 GHz radio sources in the XXL-S Field
• Radio stacking reveals evidence for star formation in the host galaxies of X-ray selected active galactic nuclei at z<1

Cited by in corpus (2)

• A super-linear "radio-AGN main sequence'' links mean radio-AGN power and galaxy stellar mass since z$\sim$3
• Hosts and environments: a (large-scale) radio history of AGN and star-forming galaxies