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10 years of LOFAR highlights: The LOFAR Two-metre Sky Survey

A detailed radio image of the entire northern sky in the frequency range of 120-168 MHz. That is what the LOFAR Two-metre Sky Survey (LoTTS) aims to achieve.

Published by the editorial team, 9 June 2020

To do that, scientists must observe no less than 3170 pointings for 8 hours each. When they achieve this impressive feat, the scientists will be able to achieve 5” resolution images with a sensitivity of 100 µJy/beam and accomplish the main scientific aims of the survey: to explore the formation and evolution of massive black holes, galaxies, clusters of galaxies and large-scale structures.

An impossible task? ‘We are now a bit over 50 percent of the observations,’ says ASTRON astronomer dr. Timothy Shimwell. Quite an achievement already and one that has been made with a team of about 250 scientists. Shimwell: ‘We’re spread over 20 countries and about 60 institutes.’

Why so many scientists? Because there were quite a few challenges to overcome with different expertises. For example: LOFAR uses supercomputers that handle large data rates, and a large number of specially written algorithms and software.

High-resolution LOFAR High Band Antenna image of the Boötes field, made at 130-169 MHz. The image is a result of the LOFAR Two Metre Sky Survey. (copyright: Wendy Williams)

To what does the ‘Two-metre’ refer? ‘To the 150 MHz-band’, Shimwell explains. So basically, to the bandwidth that LOFAR is surveying. And quite effectively, Shimwell adds. ‘One of LOFAR’s strengths is to map the sky at very low frequencies with very high resolution and sensitivity, within a reasonable amount of time.’

The project started in 2014 and has thus far produced over a hundred scientific papers. And even though the LOFAR Two-metre Sky Survey had passed the halfway mark, it is unknown when it will be finished. Shimwell: ‘Just like everyone else we have to send in proposals to get some time allocated to do our surveys. We generally put in a big proposal and on average get allocated around a thousand hours per six months.’ To put things into perspective: the whole survey will take about 14,000 hours of observations.

Particularly important about the survey is the openness, explains Shimwell: ‘We are trying to ensure that the data we collect become public in the best possible quality. That way, the whole international scientific community can benefit from it.’

On 12 June 2020, LOFAR celebrates its tenth anniversary. The radio telescope is the world’s largest low frequency instrument and is one of the pathfinders of the Square Kilometre Array (SKA), which is currently being developed. Throughout its ten years of operation, LOFAR has made some amazing discoveries. It has been a key part of groundbreaking research, both in astronomy and engineering. Here we feature some – but definitely not all – of these past highlights, with surely more to come in the future.




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