Interplanetary Scintillation studies with the Murchison Wide-field Array II: Properties of sub-arcsecond compact sources at low radio frequencies

Abstract

We report the first astrophysical application of the technique of wide-field Interplanetary Scintillation (IPS) with the Murchison Widefield Array (MWA). This powerful technique allows us to identify and measure sub-arcsecond compact components in low-frequency radio sources across large areas of sky without the need for long-baseline interferometry or ionospheric calibration. We present the results of a five-minute observation of a 30x30 sq. deg MWA field at 162 MHz with 0.5 second time resolution. Of the 2550 continuum sources detected in this field, 302 (12 per cent) show rapid fluctuations caused by IPS. We find that at least 32% of bright low-frequency radio sources contain a sub-arcsec compact component that contributes over 40% of the total flux density. Perhaps surprisingly, peaked-spectrum radio sources are the dominant population among the strongly-scintillating, low-frequency sources in our sample. While gamma-ray AGN are generally compact, flat-spectrum radio sources at higher frequencies, the 162 MHz properties of many of the Fermi blazars in our field are consistent with a compact component embedded within more extended low-frequency emission. The detection of a known pulsar in our field shows that the wide-field IPS technique is at the threshold of sensitivity needed to detect new pulsars using image plane analysis, and scaling the current MWA sensitivity to that expected for SKA-low implies that large IPS-based pulsar searches will be feasible with SKA. Calibration strategies for the SKA require a better knowledge of the space density of compact sources at low radio frequencies, which IPS observations can now provide.

Accepted for Publication in MNRAS on 27 October 2017, 21 pages, 15 figures, 5 tables, catalogue in .csv and .vot formats

References in corpus (65)

• The Wide-field Infrared Survey Explorer (WISE): Mission Description and Initial On-orbit Performance
• The ATNF Pulsar Catalogue
• LOFAR: The LOw-Frequency ARray
• The VizieR database of Astronomical Catalogues
• The ATNF Pulsar Catalogue
• The Murchison Widefield Array: the Square Kilometre Array Precursor at low radio frequencies
• The 6dF Galaxy Survey: Final Redshift Release (DR3) and Southern Large-Scale Structures
• WSClean: an implementation of a fast, generic wide-field imager for radio astronomy
• The GMRT 150 MHz All-sky Radio Survey: First Alternative Data Release TGSS ADR1
• SUMSS: A Wide-Field Radio Imaging Survey of the Southern Sky. II. The Source Catalogue
• GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) survey I: A low-frequency extragalactic catalogue
• The Third Catalog of Active Galactic Nuclei Detected by the Fermi Large Area Telescope
• The VLA Low-frequency Sky Survey
• Distant Radio Galaxies and their Environments
• The Murchison Widefield Array: Design Overview
• The Australia Telescope 20 GHz Survey: The Source Catalogue
• The 5th edition of the Roma-BZCAT. A short presentation
• A sample of radio-loud AGN in the Sloan Digital Sky Survey
• GLEAM: The GaLactic and Extragalactic All-sky MWA survey
• The Very Large Array Low-frequency Sky Survey Redux (VLSSr)
• Compact continuum source-finding for next generation radio surveys
• Near-infrared imaging and the K-z relation for radio galaxies in the 7C Redshift Survey
• Extragalactic Peaked-Spectrum Radio Sources at Low Frequencies
• On the evolution of young radio-loud AGN
• A Radio Galaxy at z=5.19
• FR II radio galaxies with z<0.3 -- I. Properties of jets, cores and hot spots
• A sample of 6C radio sources designed to find objects at redshift > 4: III --- imaging and the radio galaxy K-z relation
• The WISE gamma-ray strip parametrization: the nature of the gamma-ray Active Galactic Nuclei of Uncertain type
• The properties of extragalactic radio sources selected at 20 GHz
• The LOFAR Multifrequency Snapshot Sky Survey (MSSS) I. Survey description and first results
• Molecular Gas in the Halo Fuels the Growth of a Massive Cluster Galaxy at High Redshift
• The peculiar motions of early-type galaxies in two distant regions - II. The spectroscopic data
• The WISE properties of complete samples of radio-loud AGN
• Broadband Spectral Modeling of the Extreme Gigahertz-Peaked Spectrum Radio Source PKS B0008-421
• Parametrising Epoch of Reionization foregrounds: A deep survey of low-frequency point-source spectra with the MWA
• LBCS: the LOFAR Long-Baseline Calibrator Survey
• Physical properties in young radio sources. VLBA observations of high frequency peaking radio sources
• A sample of 6C radio sources designed to find objects at redshift > 4: II --- spectrophotometry and emission line properties
• A 98% spectroscopically complete sample of the most powerful equatorial radio sources at 408 MHz
• LOFAR imaging of Cygnus A -- Direct detection of a turnover in the hotspot radio spectra
• The Murchison Widefield Array Commissioning Survey: A Low-Frequency Catalogue of 14,110 Compact Radio Sources over 6,100 Square Degrees
• The Molonglo Southern 4 Jy sample (MS4). II. ATCA imaging and optical identification
• Wide-field VLBA Observations of the Chandra Deep Field South
• The Sub-parsec Scale Radio Properties of Southern Starburst Galaxies. I. Supernova Remnants, the Supernova Rate, and the Ionised Medium in the NGC 253 Starburst
• The Large Area Radio Galaxy Evolution Spectroscopic Survey (LARGESS): Survey design, data catalogue and GAMA/WiggleZ spectroscopy
• Nature and evolution of powerful radio galaxies and their link with the quasar luminosity function
• Interplanetary Scintillation with the Murchison Widefield Array I: A sub-arcsecond Survey over 900 square degrees at 79 and 158 MHz
• The Murchison Widefield Array Correlator
• High-energy sources at low radio frequency: the Murchison Widefield Array view of Fermi blazars
• A unified supernova catalogue
• The LOFAR long baseline snapshot calibrator survey
• A search for long-timescale, low-frequency radio transients
• The AT20G high angular resolution catalogue
• A deep, high resolution survey of the low frequency radio sky
• Low frequency spectral energy distributions of radio pulsars detected with the Murchison Widefield Array
• Time-domain and spectral properties of pulsars at 154 MHz
• A search for faint high-redshift radio galaxy candidates at 150 MHz
• What are the megahertz peaked-spectrum sources?
• A CO-rich merger shaping a powerful and hyper-luminous infrared radio galaxy at z=2: the Dragonfly Galaxy
• Detecting Pulsars with Interstellar Scintillation in Variance Images
• Spectral Properties and the Effect on Redshift Cut-off of Compact AGNs from the AT20G Survey
• Murchison Widefield Array Observations of Anomalous Variability: A Serendipitous Night-time Detection of Interplanetary Scintillation
• Interplanetary Scintillation with the Murchison Widefield Array V: An All-sky Survey of Compact Sources using a Modern Low-frequency Radio Telescope
• WISE data as a photometric redshift indicator for radio AGN
• Interplanetary Scintillation studies with the Murchison Wide-field Array III: Comparison of source counts and densities for radio sources and their sub-arcsecond components at 162 MHz

Cited by in corpus (33)

• The Phase II Murchison Widefield Array: Design Overview
• Source finding in the era of the SKA (precursors): Aegean 2.0
• Quasars That Have Transitioned from Radio-quiet to Radio-loud on Decadal Timescales Revealed by VLASS and FIRST
• Sub-arcsecond imaging with the International LOFAR Telescope: II. Completion of the LOFAR Long-Baseline Calibrator Survey
• An Anisotropic Density Turbulence Model from the Sun to 1 au Derived From Radio Observations
• Science with the Murchison Widefield Array: Phase I Results and Phase II Opportunities
• Diffuse galaxy cluster emission at 168 MHz within the Murchison Widefield Array Epoch of Reionization 0-hour field
• Spectral Variability of Radio Sources at Low Frequencies
• The GLEAM 4-Jy (G4Jy) Sample: I. Definition and the catalogue
• Interplanetary Scintillation with the Murchison Widefield Array V: An All-sky Survey of Compact Sources using a Modern Low-frequency Radio Telescope
• Extragalactic Peaked-Spectrum Radio Sources at Low-Frequencies are Young Radio Galaxies
• Tackling the Unique Challenges of Low-frequency Solar Polarimetry with the Square Kilometre Array Low Precursor: The Algorithm
• Wide-Band Spectral Variability of Peaked Spectrum Sources
• The Murchison Widefield Array Transients Survey (MWATS). A search for low frequency variability in a bright Southern hemisphere sample
• Application of Novel Interplanetary Scintillation Visualisations using LOFAR: A Case Study of Merged CMEs from September 2017
• Robust absolute solar flux density calibration for the Murchison Widefield Array
• Interplanetary Scintillation studies with the Murchison Wide-field Array III: Comparison of source counts and densities for radio sources and their sub-arcsecond components at 162 MHz
• Interplanetary Scintillation studies with the Murchison Wide-field Array IV: The hosts of sub-arcsecond compact sources at low radio frequencies
• A census of compact sources at 162MHz: first data release from the MWA Phase II IPS Survey
• High-redshift quasars at $z\ge 3$: radio variability and MPS/GPS candidates
• Comparing extragalactic megahertz-peaked spectrum and gigahertz-peaked spectrum sources
• A measurement of small-scale features using ionospheric scintillation. Comparison with refractive shift measurements
• Resolving moving heliospheric structures using interplanetary scintillation observations with the Murchison Widefield Array
• A Pilot Study of Interplanetary Scintillation with FAST
• Preparing for Solar and Heliospheric Science with the SKAO: An Indian Perspective
• The GLEAMing of the first supermassive black holes: II. A new sample of high-redshift radio galaxy candidates
• Milliarcsecond Structures of Variable Peaked-Spectrum Sources
• The Nature and Likely Redshift of GLEAM J0917-0012
• Identifying pulsar candidates in interferometric radio images using scintillation
• Searching for Pulsars, Magnetars, and Fast Radio Bursts in the Sculptor Galaxy using MeerKAT
• VLBI properties of compact interplanetary scintillators detected by the Murchison Widefield Array
• Spectral-line performance of low-frequency radio telescope arrays: SKA-Low stations
• Extremely inverted peaked spectrum radio sources