The Galactic Faraday rotation sky 2020

¹ Department of Astrophysics/IMAPP, Radboud University, PO Box 9010, 6500 GL Nijmegen, The Netherlands
e-mail: hutsch@astro.ru.nl
² Max Planck Institute for Astrophysics, Karl-Schwarzschildstr. 1, 85741 Garching, Germany
³ Ludwig-Maximilians-Universität München, Geschwister-Scholl-Platz 1, 80539 Munich, Germany
⁴ Jansky fellow of the National Radio Astronomy Observatory, 1003 Lopezville Rd, Socorro, NM 87801 USA
⁵ Department of Astronomy, University of Massachusetts, Amherst, 710 North Pleasant Street, Amherst, MA 01003, USA
⁶ Academia Sinica Institute of Astronomy and Astrophysics, 645 N. A’ohoku Place, Hilo, HI 96720, USA
⁷ Department of Physics and Astronomy, University of Calgary, 2500 University Drive NW, Calgary AB T2N 1N4, Canada
⁸ Hamburger Sternwarte, Universiät Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany
⁹ INAF – Istituto di Radioastronomia, via P. Gobetti 101, 40129 Bologna, Italy
¹⁰ U.S. Naval Research Lab, 4555 Overlook Ave., SW Washington, DC 20375, USA
¹¹ Google LLC, 1900 Reston Metro Plaza, Reston, VA 20190, USA
¹² Department of Astronomy, University of Virginia, Charlottesville, VA 22904, USA
¹³ Radio Astronomy Lab, 501 Campbell Hall #3411, University of California, Berkeley, CA 94720, USA
¹⁴ SETI Institute, 189 N Bernardo Ave #200, Mountain View, CA 94043, USA
¹⁵ Dunlap Institute for Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M5S 3H4, Canada
¹⁶ CSIRO Astronomy and Space Science, PO Box 1130, Bentley WA 6102, Australia
¹⁷ National Astronomical Observatory of Japan, NAOJ Chile, Alonso de Córdova 3788, Office 61B, 7630422, Vitacura, Santiago, Chile
¹⁸ Joint ALMA Observatory, Alonso de Córdova 3107, Vitacura, Santiago, Chile
¹⁹ Academia Sinica Institute of Astronomy and Astrophysics, ASMAB, NTU, No.1, Roosevelt Rd., Sec. 4, Taipei 10617, Taiwan, ROC
²⁰ International Centre for Radio Astronomy Research (ICRAR), Curtin University, Bentley, WA 6102, Australia
²¹ Dominion Radio Astrophysical Observatory, National Research Council of Canada, Box 248, Penticton, BC, V2A 6J9, Canada
²² Department of Astronomy and Owens Valley Radio Observatory, California Institute of Technology, Pasadena CA 91125, USA
²³ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
²⁴ Research School of Astronomy & Astrophysics, Australian National University, Canberra, ACT 2611, Australia
²⁵ Dipartimento di Fisica e Astronomia, Università degli Studi di Bologna, via P. Gobetti 93/2, 40129 Bologna, Italy
²⁶ National Centre for Radio Astrophysics, TIFR, Pune University Campus, Pune, India
²⁷ ASTRON, Netherlands Institute for Radio Astronomy, Oude Hoogeveensedijk 4, 7991 PD, Dwingeloo, The Netherlands
²⁸ Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
²⁹ School of Physical Sciences and Centre for Astrophysics & Relativity, Dublin City University, Glasnevin D09 W6Y4, Ireland
³⁰ GEPI&USN, Observatoire de Paris, CNRS, Université Paris Diderot, 5 place Jules Janssen, 92190 Meudon, France
³¹ Centre for Radio Astronomy Techniques and Technologies, Department of Physics and Electronics, Rhodes University, Grahamstown 6140, South Africa
³² INAF – Osservatorio Astronomico di Cagliari, Via della Scienza 5, 09047 Selargius (CA), Italy
³³ Harvard-Smithsonian Center for Astrophysics, 60 Garden St. MS-20, Cambridge, MA 01238, USA

Received: 3 February 2021
Accepted: 4 October 2021

Abstract

Aims. This work provides an update to existing reconstructions of the Galactic Faraday rotation sky by processing almost all Faraday rotation data sets available at the end of the year 2020. Observations of extra-Galactic sources in recent years have further illuminated the previously underconstrained southern celestial sky, as well as parts of the inner disc of the Milky Way, along with other regions. This has culminated in an all-sky data set of 55 190 data points, thereby comprising a significant expansion on the 41 330 used in previous works. At the same time, this novelty makes an updated separation of the Galactic component a promising enterprise. The increased source density allows us to present our results in a resolution of about 1.3 × 10⁻² deg² (46.8 arcmin²), which is a twofold increase compared to previous works.

Methods. As for previous Faraday rotation sky reconstructions, this work is based on information field theory, namely, a Bayesian inference scheme for field-like quantities that handles noisy and incomplete data.

Results. In contrast to previous reconstructions, we find a significantly thinner and pronounced Galactic disc with small-scale structures exceeding values of several thousand rad m⁻². The improvements can mainly be attributed to the new catalog of Faraday data, but are also supported by advances in correlation structure modeling within numerical information field theory. We also provide a detailed discussion on the statistical properties of the Faraday rotation sky and we investigate correlations with other data sets.