Low-frequency Faraday rotation measures towards pulsars using LOFAR: probing the 3D Galactic halo magnetic field
Date Issued
2019
Author(s)
Sobey, C.
•
Bilous, A. V.
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Grießmeier, J. -M.
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Hessels, J. W. T.
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Karastergiou, A.
•
Keane, E. F.
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Kondratiev, V. I.
•
Kramer, M.
•
Michilli, D.
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Noutsos, A.
•
•
Polzin, E. J.
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Stappers, B. W.
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Tan, C. M.
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van Leeuwen, J.
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Verbiest, J. P. W.
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Weltevrede, P.
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Heald, G.
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Alves, M. I. R.
•
•
Enßlin, T.
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Haverkorn, M.
•
Iacobelli, M.
•
Reich, W.
•
Van Eck, C.
Abstract
We determined Faraday rotation measures (RMs) towards 137 pulsars in the northern sky, using Low-Frequency Array (LOFAR) observations at 110-190 MHz. This low-frequency RM catalogue, the largest to date, improves the precision of existing RM measurements on average by a factor of 20 - due to the low frequency and wide bandwidth of the data, aided by the RM-synthesis method. We report RMs towards 25 pulsars for the first time. The RMs were corrected for ionospheric Faraday rotation to increase the accuracy of our catalogue to ≈0.1 rad m-2. The ionospheric RM correction is currently the largest contributor to the measurement uncertainty. In addition, we find that the Faraday dispersion functions towards pulsars are extremely Faraday thin - mostly less than 0.001 rad m-2. We use these new precise RM measurements (in combination with existing RMs, dispersion measures, and distance estimates) to estimate the scale height of the Galactic halo magnetic field: 2.0 ± 0.3 kpc for Galactic quadrants I and II above and below the Galactic plane (we also evaluate the scale height for these regions individually). Overall, our initial low-frequency catalogue provides valuable information about the 3D structure of the Galactic magnetic field.
Volume
484
Issue
3
Start page
3646
Issn Identifier
0035-8711
Ads BibCode
2019MNRAS.484.3646S
Rights
open.access
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