1 arcsecond imaging strategy for LoTSS survey using the International LOFAR Telescope

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• Haoyang Ye, Leiden Observatory, Leiden University
• Wednesday 10 May 2023, 11:00-12:00
• Battcock Meeting Room, Battcock Centre for Experimental Astrophysics.

If you have a question about this talk, please contact Will Barker.

We present the first wide area ($2.5 \times 2.5$ $\mathrm{deg}^{2$), deep (median noise of $\approx$ 80 \mu \mathrm{Jy} ${\mathrm{ beam}}}{−-1}$) LOFAR High Band Antenna image at a resolution of $1.2\times2$ arcsecond, an intermediate resolution between the best sub-arcsecond resolution achieved by the International LOFAR Telescope (ILT) and the standard 6-arcsecond resolution in the LOTSS (LOFAR Two-meter Sky Survey) image products. This is the first demonstration of the feasibility of $\sim 1’’$ imaging using ILT , which provides unique information on source morphology at physically relevant scales. It was made from an 8-hour observation of the ELAIS -N1 field, using the ILT data and the most up-to-date ILT imaging strategy. The estimated calibration and imaging time is 49,000 core hours, around 3 times longer than producing a LOTSS 6 ’’ image, but 5 times less than mapping a sub-arcsecond one. This most up-to-date ILT imaging strategy is described here, which will enable us to map the entire northern low-frequency sky at a resolution of $\sim 1’’$ arcsecond with affordable computing facilities and time. We also present a radio source catalogue containing 2263 sources detected over the $2.5 \times 2.5$ $\mathrm{deg}^2$ of the ELAIS -N1 field, with a peak intensity threshold of $5.5\sigma$. The catalogue has been cross-matched with the LOTSS deep ELAIS -N1 field radio catalogue, and its flux density and positional accuracy have been investigated and corrected accordingly. We find that $\sim$80 percent of sources which we expect to be detectable based on their peak brightness in the LoTSS 6’’ are detected in this image, which is approximately a factor of two higher than for 0.3’’ imaging in the Lockman Hole, implying there is a wealth of information on these intermediate scales.

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