Wide-field broad-band radio imaging with phased array feeds: A pilot multi-epoch continuum survey with ASKAP-BETA

• Published in: Monthly Notices of the Royal Astronomical Society
• Main Authors: Heywood, I., Bannister, Keith, Marvil, J., Allison, J.R., Ball, Lewis, Bell, M. E., Bock, D. C.-J., Brothers, M., Bunton, J. D., Chippendale, A.P., McClure-Griffiths, Naomi, Jackson, Carole, Voronkov, M.A.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Blackwell Publishing Ltd
• Subjects: South Pole; South pole
• Online Access: http://hdl.handle.net/1885/152562; https://doi.org/10.1093/mnras/stw186; https://openresearch-repository.anu.edu.au/bitstream/1885/152562/5/01_Heywood_Wide-field_broad-band_radio_2016.pdf.jpg

The Boolardy Engineering Test Array is a 6 × 12 m dish interferometer and the prototype of the Australian Square Kilometre Array Pathfinder (ASKAP), equipped with the first generation of ASKAP's phased array feed (PAF) receivers. These facilitate rapid wide-area imaging via the deployment of simultaneous multiple beams within an ∼30 deg2 field of view. By cycling the array through 12 interleaved pointing positions and using nine digitally formed beams, we effectively mimic a traditional 1 h × 108 pointing survey, covering ∼150 deg2 over 711–1015 MHz in 12 h of observing time. Three such observations were executed over the course of a week. We verify the full bandwidth continuum imaging performance and stability of the system via self-consistency checks and comparisons to existing radio data. The combined three epoch image has arcminute resolution and a 1σ thermal noise level of 375 μJy beam−1, although the effective noise is a factor of ∼3 higher due to residual sidelobe confusion. From this we derive a catalogue of 3722 discrete radio components, using the 35 per cent fractional bandwidth to measure in-band spectral indices for 1037 of them. A search for transient events reveals one significantly variable source within the survey area. The survey covers approximately two-thirds of the Spitzer South Pole Telescope Deep Field. This pilot project demonstrates the viability and potential of using PAFs to rapidly and accurately survey the sky at radio wavelengths.