New image demonstrates rapid survey capability of ASKAP
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An image generated by BETA covers |
September 2014
An image has been generated with the Boolardy Engineering Test Array (BETA) that covers 50 square degrees of the sky, revealing approximately 2000 sources and demonstrating the rapid survey capability of ASKAP.
ASKAP was designed to rapidly survey large areas of the sky at once and results from the six-antenna BETA instrument continue to confirm that ASKAP will function as intended.
Using BETA, the ASKAP Commissioning and Early Science (ACES) team has generated an image that covers 50 square degrees of sky, an area the equivalent of 250 full moons. Traditional radio telescopes can only see one full moon at a time.
“It would have been even bigger, only I accidentally overlapped the images by too much,” laments Dr Dave McConnell, head of the ACES team.
The image was made from three separate observations (7, 10 and 12 hours) at two areas in the constellation Tucana. The nine beams of the BETA instrument were arranged to create a square ‘footprint’ on the sky. For each of the two areas surveyed, a pair of pointings were chosen such that the beam centres of one fell on the inter-beam points of the other, a technique referred to as ‘interleaving’.
The image reveals approximately 2000 sources above a sensitivity of 5 sigma, which is the level of noise in the image. Across most of the image, sigma is approximately 600 micro Jansky; The image was produced by astronomer Dr Ian Heywood using a combination of CASA and MeqTrees for the processing.
“It’s not always easy to compare one telescope with another, but in general terms it would take nine times as long (about 12 days) to gather this data without the benefit of the BETA's PAFs and their wide field of view,” Dave explained.
BETA represents the first six ASKAP antennas installed with phased array feed (PAF) receivers at the Murchison Radio-astronomy Observatory (MRO), and is already providing promising results demonstrating the key features of the ASKAP design.
BETA is being used to not only prepare the team for the full fit-out of the ASKAP telescope, but is already proving to be a valuable tool for learning about how to use the novel phased array feed (PAF) receivers for radio astronomy and demonstrating the key fetures of ASKAP design.
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