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8th of December 2023
RACS-Mid catalog
by Duchesne et al.
The Australian SKA Pathfinder (ASKAP) has surveyed the sky at multiple frequencies as part of the Rapid ASKAP Continuum Survey (RACS). The RACS-mid survey was published by Duchesne et al. earlier this year, and a follow-up paper describes the first set of catalogues from RACS-mid, covering the sky below a declination of +49 degrees. The image above is of M51, a source in the highest declination strip of the survey, with observations centred at a declination of +46 degrees. Messier 51 is a majestic "grand-design" spiral galaxy, also known as the Whirlpool galaxy. M51 shows the effects of a close encounter with NGC 5195, the small galaxy at the outermost tip of one of the arms toward the top of these images. The images are the RACS-Mid image (left), VLA NVSS image (centre-left), VLA FIRST (centre-right), and Digitized Sky Survey (DSS2) optical image. The NVSS (NRAO VLA Sky Survey) observation was carried out in the VLA's D-configuration, with a minimum baseline of 35m and a maximum baseline of 1 km, whereas FIRST (Faint Images of the Radio Sky at Twenty centimetres) was conducted in the VLA's B-configuration, with a minimum baseline of 210m and a maxiumum baseline of 11 km. In contrast, ASKAP has a minimum physical baseline of 22m and a longest baseline of 6.4 km. Shorter baselines are more sensitive to extended source structure, which is why ASKAP and NVSS detect the full extent of the galaxy but FIRST does not. ASKAP's longer baselines than NVSS result in a higher angular resolution, which is why it can image the galaxy in finer detail. All RACS data products are available through the CSIRO ASKAP Science Data Archive.

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