The Southern Twenty-centimetre All-sky Polarization Survey (STAPS): Survey description and maps

¹ School of Physics and Astronomy, Yunnan University, Kunming 650500, PR China
² Department of Astrophysics/IMAPP, Radboud University, Nijmegen, PO Box 9010, 6500 GL Nijmegen, The Netherlands
³ INAF Instituto di Radioastronomia, Via Gobetti 101, 40129 Bologna, Italy
⁴ National Research Council Canada, Herzberg Research Centre for Astronomy and Astrophysics, Dominion Radio Astrophysical Observatory, PO Box 248, Penticton, BC V2A 6J9, Canada
⁵ Department of Astronomy and Astrophysics, University of California Santa Cruz, Santa Cruz, CA 95064, USA
⁶ INAF – Osservatorio Astronomico di Cagliari, Via della Scienza 5, 09047 Selargius, Italy
⁷ International Centre for Radio Astronomy Research (ICRAR), University of Western Australia, 35 Stirling Hwy, Crawley, WA 6009, Australia
⁸ National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100101, PR China

^★ Corresponding author; xhsun@ynu.edu.cn

Received: 6 December 2024
Accepted: 21 January 2025

Abstract

We present data processing and verification of the Southern Twenty-centimetre All-sky Polarization Survey (STAPS) conducted with Murriyang, the Parkes 64-m telescope. The survey covers the sky area of −89° < Dec < 0° and the frequency range of 1.3–1.8 GHz split into 1-MHz channels. STAPS was observed commensally with the S-band Polarization All-Sky Survey (S-PASS). The survey is composed of long azimuth scans, which allows us to absolutely calibrate Stokes Q and U with the data processing procedure developed for S-PASS. We obtained I, Q, and U maps on both the flux density scale (Jy beam⁻¹) and the main beam brightness temperature scale (K), for the 301 frequency channels with sufficiently good data. The temperature scale is tied to the Global Magneto-ionic Medium Survey (GMIMS) high-band north sky survey conducted with the Dominion Radio Astrophysical Observatory 26-m telescope. All the STAPS maps are smoothed to a common resolution of 20′. The root mean square (rms) noise per channel ranges from about 16 mK to 8 mK for I, and from about 8 mK to 5 mK for Q and U, at frequencies from 1.3 to 1.8 GHz. The rms noise in Q and U varies with declination and reaches minimum at declination of −89°. We also ran rotation measure (RM) synthesis and RM clean to obtain peak polarized intensity and Faraday depth maps. The whole STAPS data processing was validated by comparing flux densities of compact sources, pixel flux density versus pixel flux density for Cen A, pixel temperature versus pixel temperature for the entire survey area, and the RMs of extragalactic sources between STAPS and other measurements. The uncertainty of the flux density scale is less than 10%. STAPS delivers an L-band (λ20 cm) multifrequency polarization view of the Galaxy, and will help advance our understanding of the Galactic magnetic field and magnetized interstellar medium.