Next Article in Journal / Special Issue
The Extraordinary Linear Polarisation Structure of the Southern Centaurus A Lobe Revealed by ASKAP
Previous Article in Journal
The First- and Second-Order Fermi Acceleration Processes in BL Lacertae Objects
Previous Article in Special Issue
Magnetizing the Cosmic Web during Reionization
Article Menu

Export Article

Open AccessArticle
Galaxies 2018, 6(4), 126; https://doi.org/10.3390/galaxies6040126

Untangling Cosmic Magnetic Fields: Faraday Tomography at Metre Wavelengths with LOFAR

1
Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, D-21029 Hamburg, Germany
2
Dunlap Institute for Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M5S 3H4, Canada
3
Centre for Astrophysics Research, School of Physics, Astronomy and Mathematics, University of Hertfordshire, College Lane, Hatfield AL10 9AB, UK
4
Department of Astrophysics/IMAPP, Radboud University Nijmegen, P.O. Box 9010, 6500 GL Nijmegen, The Netherlands
5
ASTRON, The Netherlands Institute for Radio Astronomy, Postbus 2, 7990 AA Dwingeloo, The Netherlands
6
GEPI & USN, Observatoire de Paris, Université PSL, CNRS, 5 Place Jules Janssen, 92190 Meudon, France
7
INAF—Osservatorio Astronomico di Cagliari, Via della Scienza 5, 09047 Selargius (CA), Italy
8
Department of Space, Earth and Environment, Chalmers University of Technology, Onsala Space Observatory, 43992 Onsala, Sweden
9
CSIRO Astronomy and Space Science, P.O. Box 1130, Bentley 6102, Australia
*
Author to whom correspondence should be addressed.
Received: 26 October 2018 / Revised: 16 November 2018 / Accepted: 19 November 2018 / Published: 29 November 2018
(This article belongs to the Special Issue The Power of Faraday Tomography)
Full-Text   |   PDF [1222 KB, uploaded 29 November 2018]   |  
  |   Review Reports

Abstract

The technique of Faraday tomography is a key tool for the study of magnetised plasmas in the new era of broadband radio-polarisation observations. In particular, observations at metre wavelengths provide significantly better Faraday depth accuracies compared to traditional centimetre-wavelength observations. However, the effect of Faraday depolarisation makes the polarised signal very challenging to detect at metre wavelengths (MHz frequencies). In this work, Faraday tomography is used to characterise the Faraday rotation properties of polarised sources found in data from the LOFAR Two-Metre Sky Survey (LoTSS). Of the 76 extragalactic polarised sources analysed here, we find that all host a radio-loud AGN (Active Galactic Nucleus). The majority of the sources (∼64%) are large FRII radio galaxies with a median projected linear size of 710 kpc and median radio luminosity at 144 MHz of 4 × 10 26 W Hz 1 (with ∼13% of all sources having a linear size >1 Mpc). In several cases, both hotspots are detected in polarisation at an angular resolution of ∼20 . One such case allowed a study of intergalactic magnetic fields on scales of 3.4 Mpc. Other detected source types include an FRI radio galaxy and at least eight blazars. Most sources display simple Faraday spectra, but we highlight one blazar that displays a complex Faraday spectrum, with two close peaks in the Faraday dispersion function. View Full-Text
Keywords: magnetic fields; Faraday tomography; large-scale structure; AGN; Milky Way magnetic fields; Faraday tomography; large-scale structure; AGN; Milky Way
Figures

Figure 1

This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
SciFeed

Share & Cite This Article

MDPI and ACS Style

O’Sullivan, S.P.; Brüggen, M.; Van Eck, C.L.; Hardcastle, M.J.; Haverkorn, M.; Shimwell, T.W.; Tasse, C.; Vacca, V.; Horellou, C.; Heald, G. Untangling Cosmic Magnetic Fields: Faraday Tomography at Metre Wavelengths with LOFAR. Galaxies 2018, 6, 126.

Show more citation formats Show less citations formats

Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Related Articles

Article Metrics

Article Access Statistics

1

Comments

[Return to top]
Galaxies EISSN 2075-4434 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
Back to Top