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, K. W., Marvil, J., Allison, J. R., Ball, L., Bell, M. E., Bock, D. C.-J., Brothers, M., Bunton, J. D., Chippendale, A. P., Cooray, F., Cornwell, T. J., De Boer, D., Edwards, P., Gough, R., Gupta, N., Harvey-Smith, L., Hay, S., Hotan, A. W., Indermuehle, B., Jacka, C., Jackson, C. A., Johnston, S., Kimball, A. E., Koribalski, B. S., Lenc, E., Macleod, A., McClure-Griffiths, N., McConnell, D., Mirtschin, P., Murphy, T., Neuhold, S., Norris, R. P., Pearce, S., Popping, A., Qiao, R. Y., Reynolds, J. E., Sadler, E. M., Sault, R. J., Schinckel, A. E. T., Serra, P., Shimwell, T. W., Stevens, J., Tuthill, J., Tzioumis, A., Voronkov, M. A., Westmeier, T., Whiting, M. T.
• Format: Text
• Language: English
• Published: Oxford University Press 2016
• Subjects: Article; South Pole; South pole
• Online Access: http://mnras.oxfordjournals.org/cgi/content/short/457/4/4160; https://doi.org/10.1093/mnras/stw186

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.