Interplanetary scintillation studies with the Murchison Widefield Array - II. Properties of sub-arcsecond compact sources at low radio frequencies
MetadataShow full item record
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2018 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
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.
Showing items related by title, author, creator and subject.
Murchison widefield array observations of anomalous variability: A serendipitous night-time detection of interplanetary scintillationKaplan, D.; Tingay, Steven; Manoharan, P.; Macquart, Jean-Pierre; Hancock, Paul; Morgan, John; Mitchell, D.; Ekers, R.; Wayth, Randall; Trott, Cathryn; Murphy, T.; Oberoi, D.; Cairns, I.; Feng, L.; Kudryavtseva, N.; Bernardi, G.; Bowman, J.; Briggs, F.; Cappallo, R.; Deshpande, A.; Gaensler, B.; Greenhill, L.; Hurley Walker, Natasha; Hazelton, B.; Johnston Hollitt, M.; Lonsdale, C.; McWhirter, S.; Morales, M.; Morgan, E.; Ord, S.; Prabu, T.; Udaya Shankar, N.; Srivani, K.; Subrahmanyan, R.; Webster, R.; Williams, A.; Williams, C. (2015)We present observations of high-amplitude rapid (2 s) variability toward two bright, compact extragalactic radio sources out of several hundred of the brightest radio sources in one of the Murchison Widefield Array (MWA) ...
Lenc, E.; Garrett, M.; Wucknitz, O.; Anderson, J.; Tingay, Steven (2008)We report on the first wide-field, very long baseline interferometry (VLBI) survey at 90 cm. The survey area consists of two overlapping 28 deg2 fields centered on the quasar J0226+3421 and the gravitational lens B0218+357. ...
Koay, Jun Yi (2012)The scattering of radio waves and multipath propagation in the interstellar medium (ISM) of our Galaxy produces various observable phenomena such as the interstellar scintillation (ISS) and angular broadening of compact ...