Rapid ASKAP Continuum Survey

Rapid ASKAP Continuum Survey
Name	Rapid ASKAP Continuum Survey
Abbreviation	RACS
Telescope	Australian Square Kilometre Array Pathfinder
Operators	Commonwealth Scientific and Industrial Research Organisation
Start date	2019
Frequency	0.7–1.8 GHz
Sky coverage	Southern Hemisphere, full-sky goals
Resolution	~10–25 arcsec
Sensitivity	~0.25–1 mJy beam−1

Rapid ASKAP Continuum Survey is a large-area radio continuum survey conducted with the Australian Square Kilometre Array Pathfinder. It provides wide-field imaging across the Southern Hemisphere and adjacent equatorial regions, delivering source catalogues and images that underpin research by teams associated with the Commonwealth Scientific and Industrial Research Organisation, the International Centre for Radio Astronomy Research, and partner universities. The survey connects to multiwavelength programmes led by institutions such as the European Southern Observatory, the National Aeronautics and Space Administration, and the Max Planck Society.

Overview

RACS was conceived to deliver an all-sky radio continuum map using the Australian Square Kilometre Array Pathfinder, building on precursor surveys like the NRAO VLA Sky Survey, the Faint Images of the Radio Sky at Twenty-Centimeters project, and the Sydney University Molonglo Sky Survey, while complementing contemporaneous efforts by the Low-Frequency Array, the MeerKAT telescope, and the Karl G. Jansky Very Large Array. The project involves collaborations among the Commonwealth Scientific and Industrial Research Organisation, Curtin University, the University of Western Australia, and international partners including the University of Cambridge and the Max Planck Institute for Radio Astronomy. RACS provides uniform coverage to support surveys by the Large Synoptic Survey Telescope, the Dark Energy Survey, and the Gaia mission.

Instrumentation and Observing Strategy

Observations use the Australian Square Kilometre Array Pathfinder equipped with phased array feeds developed through collaborations involving CSIRO, the Australian National University, and the Commonwealth Scientific and Industrial Research Organisation Engineering team. The ASKAP array employs 36 12-metre antennas located at the Murchison Radio-astronomy Observatory, an infrastructure overseen by the Pawsey Supercomputing Centre and supported by state agencies from Western Australia. The observing strategy utilises rapid mosaicking, multiple frequency tunings across ~0.7–1.8 GHz, and beam-forming techniques influenced by developments from the Square Kilometre Array Organisation, the European Space Agency, and the Jet Propulsion Laboratory. Scheduling and calibration procedures draw on algorithms and operational experience from the Very Large Array, the Atacama Large Millimeter/submillimeter Array, and the MeerKAT operations teams.

Data Processing and Calibration

Data processing leverages high-performance computing resources at the Pawsey Supercomputing Centre and software pipelines developed by CSIRO in collaboration with the International Centre for Radio Astronomy Research, the University of Oxford, and the University of Cambridge. Calibration uses sky models informed by the Molonglo Reference Catalogue, the TIFR GMRT Sky Survey, and the GLEAM survey led by Curtin University and the University of Sydney, while direction-dependent calibration schemes incorporate methods pioneered by the LOFAR Surveys Key Science Project and the CASA package maintained by the National Radio Astronomy Observatory. Quality assurance and verification involve cross-matches with catalogues from the Sloan Digital Sky Survey, the Two Micron All Sky Survey, the Wide-field Infrared Survey Explorer, and the Pan-STARRS1 Science Consortium.

Survey Products and Data Release

RACS delivers source catalogues, image mosaics, and value-added products that are disseminated via archival systems operated by CSIRO, the Australian National Data Service, and international partners including the European Southern Observatory archive and the NASA/IPAC Infrared Science Archive. Data releases have been coordinated with teams from the International Centre for Radio Astronomy Research, the University of Oxford, and the Max Planck Institute for Astrophysics, providing data formats compatible with Virtual Observatory standards promulgated by the International Virtual Observatory Alliance. Products include continuum images, spectral index maps, and transient candidate lists useful for follow-up with the Very Large Telescope, the Hubble Space Telescope, and the Cherenkov Telescope Array collaborations.

Scientific Goals and Key Results

Primary scientific aims include characterising radio source populations relevant to active galactic nuclei studied by teams at the Harvard-Smithsonian Center for Astrophysics and the Max Planck Institute for Extraterrestrial Physics, mapping star-formation traced in synergy with the Herschel Space Observatory and the Spitzer Space Telescope, and identifying transients for follow-up by the Laser Interferometer Gravitational-Wave Observatory and the Fermi Gamma-ray Space Telescope teams. Early results have produced source catalogues used by groups at the University of Cambridge, the University of Melbourne, and the University of Sydney to study radio-loud quasars, supernova remnants, and radio galaxies comparable to objects in the Third Cambridge Catalogue and the Parkes Catalogue. Cross-correlation studies with the Dark Energy Survey and the Sloan Digital Sky Survey have enabled cosmological investigations pursued by researchers at the University of Chicago and the Kavli Institute.

Challenges and Future Developments

Challenges include mitigating radio frequency interference encountered at the Murchison Radio-astronomy Observatory and integrating direction-dependent calibration to reach the dynamic range goals set by the Square Kilometre Array Organisation, the International Centre for Radio Astronomy Research, and partner institutions such as the University of Oxford. Future developments envisage deeper, higher-resolution follow-ups using ASKAP upgrades, coordinated campaigns with MeerKAT and the SKA Observatory, and enhanced machine-learning classification pipelines developed in collaboration with researchers at Carnegie Mellon University and the Massachusetts Institute of Technology. Continued synergy with facilities including the European Southern Observatory, the National Radio Astronomy Observatory, and the Pawsey Supercomputing Centre will expand the scientific legacy of the survey.

Category:Radio astronomy projects Category:Australian Square Kilometre Array Pathfinder