The Rapid ASKAP Continuum Survey III: Spectra and Polarisation In Cutouts of Extragalactic Sources (SPICE-RACS) First Data Release

Alec J. M. Thomson; David McConnell; Emil Lenc; Timothy J Galvin; Lawrence Rudnick; George Heald; Catherine L. Hale; Stefan W. Duchesne; Craig S. Anderson; Ettore Carretti; Christoph Federrath; B. M. Gaensler; Lisa Harvey-Smith; Marijke Haverkorn; Aidan W. Hotan; Yik Ki Ma; Tara Murphy; N. M. McClure-Griffith; Vanessa A. Moss; Shane P. O'Sullivan; Wasim Raja; Amit Seta; Cameron L. Van Eck; Jennifer L. West; Matthew T. Whiting; Mark H. Wieringa

arXiv · 2307.07207

The Rapid ASKAP Continuum Survey III: Spectra and Polarisation In Cutouts of Extragalactic Sources (SPICE-RACS) First Data Release

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Abstract

The Australian SKA Pathfinder (ASKAP) radio telescope has carried out a survey of the entire Southern Sky at 887.5MHz. The wide area, high angular resolution, and broad bandwidth provided by the low-band Rapid ASKAP Continuum Survey (RACS-low) allow the production of a next-generation rotation measure (RM) grid across the entire Southern Sky. Here we introduce this project as Spectral and Polarisation in Cutouts of Extragalactic sources from RACS (SPICE-RACS). In our first data release, we image 30 RACS-low fields in Stokes $I$, $Q$, $U$ at 25'' angular resolution, across 744 to 1032MHz with 1MHz spectral resolution. Using a bespoke, highly parallelised, software pipeline we are able to rapidly process wide-area spectro-polarimetric ASKAP observations. Notably, we use 'postage stamp' cutouts to assess the polarisation properties of \ncomponents\ radio components detected in total intensity. We find that our Stokes $Q$ and $U$ images have an rms noise of ~80$\mu$Jy/PSF, and our correction for instrumental polarisation leakage allows us to characterise components with >1% polarisation fraction over most of the field of view. We produce a broadband polarised radio component catalogue that contains \nrms\ RM measurements over an area of ~1300deg^2 with an average error in RM of 1.6+1.1-1.0rad/m^2, and an average linear polarisation fraction 3.4+3.0-1.6%. We determine this subset of components using the conditions that the polarised signal-to-noise ratio is $>8$, the polarisation fraction is above our estimated polarised leakage, and the Stokes $I$ spectrum has a reliable model. Our catalogue provides an areal density of $4\pm2$ RMs/deg^2; an increase of $\sim4$ times over the previous state-of-the-art (Taylor et al. 2009). Meaning that, having used just 3% of the RACS-low sky area, we have produced the 3rd largest RM catalogue to date. This catalogue has broad applications for studying...

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Alec J. M. Thomson, David McConnell, Emil Lenc, Timothy J Galvin, Lawrence Rudnick, George Heald, Catherine L. Hale, Stefan W. Duchesne, Craig S. Anderson, Ettore Carretti, Christoph Federrath, B. M. Gaensler, Lisa Harvey-Smith, Marijke Haverkorn, Aidan W. Hotan, Yik Ki Ma, Tara Murphy, N. M. McClure-Griffith, Vanessa A. Moss, Shane P. O'Sullivan, Wasim Raja, Amit Seta, Cameron L. Van Eck, Jennifer L. West, Matthew T. Whiting, Mark H. Wieringa. 2023-07-14. The Rapid ASKAP Continuum Survey III: Spectra and Polarisation In Cutouts of Extragalactic Sources (SPICE-RACS) First Data Release. https://arxiv.org/abs/2307.07207

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