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'SullivanWasim Raja, Amit Seta, Cameron L. Van Eck, Jennifer L. West, Matthew T. Whiting, Mark H. Wieringa

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

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 ~80μJy/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±2 RMs/deg^2; an increase of ∼4 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...
Original languageEnglish
Article numbere040
Pages (from-to)1-37
Number of pages37
JournalPublications of the Astronomical Society of Australia
Publication statusPublished - 30 Aug 2023

Keywords / Materials (for Non-textual outputs)

  • ISM: magnetic fields
  • Radio continuum: general
  • galaxies: magnetic fields
  • magnetic fields
  • polarisation
  • radio continuum: galaxies


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