What are the megahertz peaked-spectrum sources?

Abstract

Megahertz peaked-spectrum (MPS) sources have spectra that peak at frequencies below 1 GHz in the observer's frame and are believed to be radio-loud active galactic nuclei (AGN). We recently presented a new method to search for high-redshift AGN by identifying unusually compact MPS sources. In this paper, we present European VLBI Network (EVN) observations of 11 MPS sources which we use to determine their sizes and investigate the nature of the sources with ~10 mas resolution. Of the 11 sources, we detect nine with the EVN. Combining the EVN observations with spectral and redshift information, we show that the detected sources are all AGN with linear sizes smaller than 1.1 kpc and are likely young. This shows that low-frequency colour-colour diagrams are an easy and efficient way of selecting small AGN and explains our high detection fraction (82%) in comparison to comparable surveys. Finally we argue that the detected sources are all likely compact symmetric objects and that none of the sources are blazars.

arXiv comment20 pages, 9 figures, 5 tables, accepted for publication in MNRAS

References in corpus (49)

• Observational Evidence of AGN Feedback
• LOFAR: The LOw-Frequency ARray
• EAZY: A Fast, Public Photometric Redshift Code
• A luminous quasar at a redshift of z = 7.085
• The Tenth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the SDSS-III Apache Point Observatory Galactic Evolution Experiment
• Distant Radio Galaxies and their Environments
• Sub-milliarcsecond Imaging of Quasars and Active Galactic Nuclei. IV. Fine Scale Structure
• Ionospheric Calibration of Low Frequency Radio Interferometric Observations using the Peeling Scheme: I. Method Description and First Results
• Radio galaxies with a `double-double' morphology: I - Analysis of the radio properties and evidence for interrupted activity in active galactic nuclei
• A broadband flux scale for low frequency radio telescopes
• Radio Jets Clearing the Way Through a Galaxy: Watching Feedback in Action
• AGES: The AGN and Galaxy Evolution Survey
• On the evolution of young radio-loud AGN
• XBootes: An X-Ray Survey of the NDWFS Bootes Field - Paper I Overview and Initial Results
• Intrinsic Brightness Temperatures of AGN Jets
• A new double radio relic in PSZ1 G096.89+24.17 and a radio relic mass-luminosity relation
• Spectral Ages of CSOs and CSS Sources
• Deep Westerbork 1.4 GHz Imaging of the Bootes Field
• A Deep VLA survey at 20cm of the ISO ELAIS survey regions
• A giant radio halo in the cool core cluster CL1821+643
• VLBI observations of 10 CSO candidates: expansion velocities of hot spots
• The Chandra XBootes Survey - III: Optical and Near-IR Counterparts
• Physical properties in young radio sources. VLBA observations of high frequency peaking radio sources
• Low Resolution Spectral Templates For Galaxies From 0.2 -- 10 microns
• A sample of 6C radio sources designed to find objects at redshift > 4: II --- spectrophotometry and emission line properties
• Evolution of faint radio sources in the VIDEO-XMM3 field
• Constraining the nature of High Frequency Peakers. I. The spectral variability
• mJIVE-20: a survey for compact mJy radio objects with the Very Long Baseline Array
• New Insights on the z-alpha Correlation from Complete Radio Samples
• Unveiling the nature of the unidentified gamma-ray sources III: gamma-ray blazar-like counterparts at low radio frequencies
• Wide-field VLBA Observations of the Chandra Deep Field South
• The first estimate of radio jet proper motion at z>5
• T-RaMiSu: The Two-meter Radio Mini Survey I. The Bootes Field
• Intermittent jet activity in the radio galaxy 4C29.30?
• Nature and evolution of powerful radio galaxies and their link with the quasar luminosity function
• Compact radio cores: from the first black holes to the last
• Multiwavelength characterization of faint Ultra Steep Spectrum radio sources : A search for high-redshift radio galaxies
• A search for AGN in the most extreme UV-selected starbursts using the European VLBI Network
• LOFAR low-band antenna observations of the 3C295 and Bootes fields: source counts and ultra-steep spectrum sources
• Deep VLBI Imaging of Faint Radio Sources in the NOAO Bootes Field
• The 6C** sample of steep-spectrum radio sources: I - Radio data, near-infrared imaging and optical spectroscopy
• The VLA-COSMOS Survey: V. 324 MHz continuum observations
• A search for distant radio galaxies from SUMSS and NVSS: II. Optical Spectroscopy
• AGN duty cycle estimates for the ultra-steep spectrum radio relic VLSS J1431.8+1331
• The PEP Survey: Infrared Properties of Radio-Selected AGN
• Synchrotron Spectra and Ages of Compact Steep Spectrum Radio Sources
• A Wide Field, Low Frequency Radio Image of the Field of M31: II. -- Source Classification and Discussion
• BL Lac Objects and Blazars: Past, Present, and Future
• X-ray Identifications of FIRST Radio Sources in the xBootes Field

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• The Lockman Hole project: LOFAR observations and spectral index properties of low-frequency radio sources
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• Interplanetary Scintillation studies with the Murchison Wide-field Array II: Properties of sub-arcsecond compact sources at low radio frequencies
• Extragalactic megahertz-peaked spectrum radio sources at milliarcsecond scales
• High-redshift quasars at $z\ge 3$ -- I. Radio spectra
• Multifrequency study of GHz-peaked spectrum sources
• Spectral Variability of Radio Sources at Low Frequencies
• Radio Spectra of Luminous, Heavily Obscured WISE-NVSS Selected Quasars
• The LOFAR Two Metre Sky Survey: Deep Fields. II. The ELAIS-N1 LOFAR deep field
• Variability and parsec-scale radio structure of candidate compact symmetric objects
• Optical Properties of Peaked Spectrum Radio Sources
• The LOFAR LBA Sky Survey: Deep Fields I. The Boötes Field
• High-redshift quasars at $z\ge 3$: radio variability and MPS/GPS candidates
• Radio observations of four active galactic nuclei hosting intermediate-mass black hole candidates: studying the outflow activity and evolution
• GMRT observations of extragalactic radio sources with steeply inverted spectra
• The GLEAMing of the first supermassive black holes: II. A new sample of high-redshift radio galaxy candidates
• A new distant Giant Radio Galaxy in the Boötes field serendipitously detected by Chandra
• Radio properties of high-redshift galaxies at $z\ge 1$
• A Multi-Mechanism Hybrid Model of Peaked-Spectrum Radio Sources
• High-resolution observations of low-luminosity peaked spectrum sources
• The evolution of extragalactic peaked-spectrum sources down to 54 megahertz