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  1. OA@INAF
  2. PRODOTTI RICERCA INAF
  3. 1 CONTRIBUTI IN RIVISTE (Journal articles)
  4. 1.01 Articoli in rivista
Please use this identifier to cite or link to this item: http://hdl.handle.net/20.500.12386/28074
Title: Untangling Cosmic Magnetic Fields: Faraday Tomography at Metre Wavelengths with LOFAR
Authors: O'Sullivan, Shane
Brüggen, Marcus
Van Eck, Cameron
Hardcastle, Martin
Haverkorn, Marijke
Shimwell, Timothy
Tasse, Cyril
VACCA, VALENTINA 
Horellou, Cathy
Heald, George
Issue Date: 2018
Journal: GALAXIES 
Number: 6
Issue: 4
First Page: 126
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 <mml:math display="inline"> <mml:mrow> <mml:mn>4</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mn>10</mml:mn> <mml:mn>26</mml:mn> </mml:msup> </mml:mrow> </mml:math> W Hz<mml:math display="inline"><mml:msup><mml:mrow></mml:mrow> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:math> (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<mml:math display="inline"><mml:msup><mml:mrow></mml:mrow><mml:mrow><mml:mo>″</mml:mo> </mml:mrow> </mml:msup> </mml:math>. 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.
URI: http://hdl.handle.net/20.500.12386/28074
URL: https://www.mdpi.com/2075-4434/6/4/126
ISSN: 2075-4434
DOI: 10.3390/galaxies6040126
Bibcode ADS: 2018Galax...6..126O
Fulltext: open
Appears in Collections:1.01 Articoli in rivista

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1811.12732.pdf1.24 MBAdobe PDFView/Open
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