On the nature of bright compact radio sources at z>4.5

Abstract

High-redshift radio-loud quasars are used to, among other things, test the predictions of cosmological models, set constraints on black hole growth in the early universe and understand galaxy evolution. Prior to this paper, 20 extragalactic radio sources at redshifts above 4.5 have been imaged with very long baseline interferometry (VLBI). Here we report on observations of an additional ten z>4.5 sources at 1.7 and 5 GHz with the European VLBI Network (EVN), thereby increasing the number of imaged sources by 50%. Combining our newly observed sources with those from the literature, we create a substantial sample of 30 z>4.5 VLBI sources, allowing us to study the nature of these objects. Using spectral indices, variability and brightness temperatures, we conclude that of the 27 sources with sufficient information to classify, the radio emission from one source is from star formation, 13 are flat-spectrum radio quasars and 13 are steep-spectrum sources. We also argue that the steep-spectrum sources are off-axis (unbeamed) radio sources with rest-frame self-absorption peaks at or below GHz frequencies and that these sources can be classified as gigahertz peaked-spectrum (GPS) and megahertz peaked-spectrum (MPS) sources.

arXiv commentAccepted for publication in Monthly Notices of the Royal Astronomical Society, 18 pages, 1 figure, 7 tables

References in corpus (51)

• Observational Evidence of AGN Feedback
• 21-cm cosmology
• The host galaxies of radio-loud AGN: mass dependencies, gas cooling and AGN feedback
• Sub-milliarcsecond Imaging of Quasars and Active Galactic Nuclei. IV. Fine Scale Structure
• The VLBA Calibrator Survey - VCS1
• Radio and Millimeter Continuum Surveys and their Astrophysical Implications
• The Sloan Digital Sky Survey quasar catalog: tenth data release
• Resolving the Radio Source Background: Deeper Understanding Through Confusion
• The VLBA Imaging and Polarimetry Survey at 5 GHz
• Radio Jets Clearing the Way Through a Galaxy: Watching Feedback in Action
• The Half Million Quasars (HMQ) Catalogue
• The Sixth VLBA Calibrator Survey: VCS6
• The Fourth VLBA Calibrator Survey - VCS4
• The Micro-Arcsecond Scintillation-Induced Variability (MASIV) Survey II: The First Four Epochs
• A 250 GHz Survey of High Redshift QSOs from the Sloan Digital Sky Survey
• Q0906+6930: The Highest-Redshift Blazar
• Blazars in the early Universe
• Sensitive observations at 1.4 and 250 GHz of z > 5 QSOs
• VLBI observations of 10 CSO candidates: expansion velocities of hot spots
• Evolution of faint radio sources in the VIDEO-XMM3 field
• The first estimate of radio jet proper motion at z>5
• Wide-field VLBA Observations of the Chandra Deep Field South
• Modeling the Counts of Faint Radio Loud Quasars: Constraints on the Supermassive Black Hole Population and Predictions for High Redshift
• Into the central 10 pc of the most distant known radio quasar. VLBI imaging observations of J1429+5447 at z=6.21
• Photon Trapping Enables Super-Eddington Growth of Black-Hole Seeds in Galaxies at High Redshift
• High-resolution double morphology of the most distant known radio quasar at z=6.12
• X-rays from the redshift 7.1 quasar ULAS J1120+0641
• Optical-radio positional offsets for active galactic nuclei
• High-resolution radio imaging of the most distant radio quasar SDSS J0836+0054
• VLA and VLBA Observations of the Highest Redshift Radio-Loud QSO J1427+3312 at z = 6.12
• Do high redshift quasars have powerful jets?
• Radio structure of the most distant radio-detected quasar at the ten milli- arcsecond scale
• A search for AGN in the most extreme UV-selected starbursts using the European VLBI Network
• Effect of asymmetry of the radio source distribution on the apparent proper motion kinematic analysis
• VLBI observations of the radio quasar J2228+0110 at z=5.95 and other field sources in multiple-phase-centre mode
• Discovery of a Kiloparsec Scale X-ray/Radio Jet in the z=4.72 Quasar GB 1428+4217
• Variability of the extreme z=4.72 blazar, GB 1428+4217
• On the coherence loss in phase-referenced VLBI observations
• High-resolution images of five radio quasars at early cosmological epochs
• What are the megahertz peaked-spectrum sources?
• Physical parameters of a relativistic jet at very high redshift: the case of the blazar J1430+4204
• The PEP Survey: Infrared Properties of Radio-Selected AGN
• Dual-Frequency Observations of 140 Compact, Flat-Spectrum Active Galactic Nuclei for Scintillation-Induced Variability
• Dark bubbles around high-redshift radio-loud AGN
• Sensitive VLBI Observations of the z = 4.7 QSO BRI 1202-0725
• VLBA observations of z > 4 radio-loud quasars
• VLBI observation of the newly discovered z=5.18 quasar SDSS J0131-0321
• On the Doppler boosting in the compact radio jet of the distant blazar J1026+2542 at z=5.3
• Why Do Compact Active Galactic Nuclei at High Redshift Scintillate Less?
• BL Lac Objects and Blazars: Past, Present, and Future
• Optical Characteristics of the Astrometric Radio Sources

Cited by in corpus (40)

• Compact steep-spectrum and peaked-spectrum radio sources
• The first blazar observed at z>6
• Measurements of the Hubble constant and cosmic curvature with quasars: ultra-compact radio structure and strong gravitational lensing
• Evolving parsec-scale radio structure in the most distant blazar known
• First constraints on the AGN X-ray luminosity function at $z\sim 6$ from an eROSITA-detected quasar
• Blazars at the Cosmic Dawn
• The space density of z>4 blazars
• High-redshift quasars at $z\ge 3$ -- I. Radio spectra
• J0906+6930: a radio-loud quasar in the early Universe
• Multifrequency study of GHz-peaked spectrum sources
• A new version of the OCARS catalog of Optical Characteristics of Astrometric Radio Sources
• Constraining the radio jet proper motion of the high-redshift quasar J2134-0419 at z=4.3
• Fast jet proper motion discovered in a blazar at z = 4.72
• Radio-loud Quasars above Redshift 4: VLBI Imaging of an Extended Sample
• Radio spectra of bright compact sources at z>4.5
• The MAVERIC survey: A hidden pulsar and a black hole candidate in ATCA radio imaging of the globular cluster NGC 6397
• VLBI observations of four radio quasars at $z>4$: blazars or not?
• Radio Jet Proper-motion Analysis of Nine Distant Quasars above Redshift 3.5
• X-ray Properties of Young Radio Quasars at z > 4.5
• The hyperluminous, dust-obscured quasar W2246-0526 at z=4.6: detection of parsec-scale radio activity
• High-resolution radio imaging of two luminous quasars beyond redshift 4.5
• The extremely X-ray luminous radio-loud quasar CFHQS J142952+544717 at $z=6.18$ under Chandra high-angular resolution lens
• Flux-density measurements of the high-redshift blazar PSO J047.4478+27.2992 at 4.7 and 8.2 GHz with RATAN-600
• High-redshift quasars at $z\ge 3$: radio variability and MPS/GPS candidates
• J2102+6015: a young radio source at z = 4.575
• High-$z$ radio Quasars in RACS I: Selection, identification, and multi-wavelength properties
• Revealing faint compact radio jets at redshifts above 5 with very long baseline interferometry
• The loud and the quiet: searching for radio counterparts of two radio-weak BL Lac candidates with VLBI
• Very long baseline interferometry observations of the high-redshift blazar candidate J0141-5427
• A small radio galaxy at z=4.026
• The GLEAMing of the first supermassive black holes: II. A new sample of high-redshift radio galaxy candidates
• Multi-scale Radio and X-ray Structure of the High-redshift Quasar PMN J0909+0354
• Revisiting a Core-Jet Laboratory at High Redshift: Analysis of the Radio Jet in the Quasar PKS 2215+020 at z=3.572
• Radio properties of high-redshift galaxies at $z\ge 1$
• Magnetic Reconnection as a Potential Driver of X-ray Variability in Active Galactic Nuclei
• Cosmological test using the high-redshift detection rate of FSRQs with the Square Kilometer Array
• A Multi-Mechanism Hybrid Model of Peaked-Spectrum Radio Sources
• High-resolution observations of low-luminosity peaked spectrum sources
• J2102+6015: an Intriguing Radio-loud Active Galactic Nucleus in the Early Universe
• Milliarcsecond-resolution Radio-imaging Survey of Blazar Candidates at 4 < z < 5.4