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26th of August 2019
MWA observations of scintillating sources
by Sadler et al.
Around 10 per cent of bright low-frequency radio sources observed with the Murchison Widefield Array (MWA) show strong interplanetary scintillation (IPS) on time-scales of a few seconds, implying that almost all their low-frequency radio emission comes from a compact component less than 0.5 arcsec in angular size. Most of these objects are compact steep spectrum or MHz-peaked spectrum radio sources. Sadler et al. used mid-infrared data from the Wide-field Infrared Survey Explorer (WISE) catalogue to search for the host galaxies of 65 strongly scintillating MWA sources and compare their properties with those of the overall population of bright low-frequency radio sources. The strongly scintillating sources are found to be more distant than others, indicating that the widefield IPS technique has the potential to provide a powerful new tool for identifying high-redshift radio galaxies.

The image above shows an example of the overlay plots used to assist identification of MWA sources. Grey-scale images show the WISE band 1 (3.4 μm) and band 2 (4.6 μm) data, with radio contours overlaid on the band 1 image. Red contours correspond to the 162 MHz MWA data and blue contours to the higher-resolution VLA FIRST data. A cyan cross marks the FIRST (VLA survey) radio centroid, and orange circles mark mid-IR sources listed in the AllWISE catalogue. The WISE source closest to the radio centroid was accepted as a genuine ID. More details are given in the paper by Sadler et al. published in the Monthly Notices of the Royal Astronomical Society.

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