Chhetri et al. present a catalogue of 131 compact (angular size less than 0.1 arcseconds) sources detected with ASKAP at 823 MHz via their Interplanetary Scintillation (IPS).  These measurements were made across the full ASKAP field of view of 35 square degrees, utilising all 36 Phased Array Feed (PAF) beams. To bypass ASKAP’s standard correlator’s minimum integration limit of 10 seconds, the team used the CRAFT data capture system (CRACO), with visibilities sampled every 110 milli-seconds.  The paper presents the data processing steps, the sources detected, and their IPS-inferred properties. ASKAP IPS cleanly separates two populations: compact hot spots embedded in extended lobes and IPS-unresolved sources which are Active Galactic Nuclei or Compact Symmetric Objects. They also compare these results with the results from observations of IPS at 162 MHz with the Murchison Widefield Array, providing the spectra of compact components between 162 MHz and 888 MHz. These measurements further re-enforce the dominance of peaked-spectrum SEDs in the compact-source population at frequencies below 1 GHz. This pilot study using test data is a pathfinder for a more comprehensive ASKAP IPS survey which is underway.

The images above show the inner part of the standard image for one ASKAP beam (left), and the corresponding variability image in the same area (right). The images are one degree across. The change in the density of sources is apparent — compact sources showing high level of scintillation are identified with green circles.