The magnetized disk-halo transition region of M51

Kierdorf M, Mao SA, Beck R, Basu A, Fletcher A, Horellou C, Tabatabaei F, Ott J, Haverkorn M (2020)
Astronomy and Astrophysics 642: A118.

Zeitschriftenaufsatz | Veröffentlicht | Englisch
 
Download
Es wurden keine Dateien hochgeladen. Nur Publikationsnachweis!
Autor*in
Kierdorf, M.; Mao, S. A.; Beck, R.; Basu, AritraUniBi; Fletcher, A.; Horellou, C.; Tabatabaei, F.; Ott, J.; Haverkorn, M.
Abstract / Bemerkung
The grand-design face-on spiral galaxy M 51 is an excellent laboratory for studying magnetic fields in galaxies. Due to wavelength-dependent Faraday depolarization, linearly polarized synchrotron emission at different radio frequencies yields a picture of the galaxy at different depths: observations in the L-band (1-2 GHz) probe the halo region, while at 4.85 GHz (C-band) and 8.35 GHz (X-band), the linearly polarized emission mostly emerges from the disk region of M 51. We present new observations of M 51 using the Karl G. Jansky Very Large Array at the intermediate frequency range of the S-band (2-4 GHz), where previously no high-resolution broadband polarization observations existed, to shed new light on the transition region between the disk and the halo. We present the S-band radio images of the distributions of the total intensity, polarized intensity, degree of polarization, and rotation measure (RM). The RM distribution in the S-band shows a fluctuating pattern without any apparent large-scale structure. We discuss a model of the depolarization of synchrotron radiation in a multi-layer magneto-ionic medium and compare the model predictions to the multi-frequency polarization data of M 51 between 1-8 GHz. The model makes distinct predictions of a two-layer (disk-halo) and three-layer (far-side halo "disk" near-side halo) system. Since the model predictions strongly differ within the wavelength range of the S-band, the new S-band data are essential for distinguishing between the different systems. A two-layer model of M 51 is preferred. The parameters of the model are adjusted to fit to the data of polarization fractions in a few selected regions. In three spiral arm regions, the turbulent field in the disk dominates with strengths between 18 mu G and 24 mu G, while the regular field strengths are 8-16 mu G. In one inter-arm region, the regular field strength of 18 mu G exceeds that of the turbulent field of 11 mu G. The regular field strengths in the halo are 3-5 mu G. The observed RMs in the disk-halo transition region are probably dominated by tangled regular fields, as predicted from models of evolving dynamos, and/or vertical fields, as predicted from numerical simulations of Parker instabilities or galactic winds. Both types of magnetic fields have frequent reversals on scales similar to or larger than the beam size (similar to 550 pc) that contribute to an increase of the RM dispersion and to distortions of any large-scale pattern of the regular field. Our study devises new ways of analyzing and interpreting broadband multi-frequency polarization data that will be applicable to future data from, for example, the Square Kilometre Array.
Stichworte
galaxies: general; galaxies: magnetic fields; galaxies: individual: M; 51; galaxies: ISM
Erscheinungsjahr
2020
Zeitschriftentitel
Astronomy and Astrophysics
Band
642
Art.-Nr.
A118
ISSN
0004-6361
eISSN
1432-0746
Page URI
https://pub.uni-bielefeld.de/record/2949207

Zitieren

Kierdorf M, Mao SA, Beck R, et al. The magnetized disk-halo transition region of M51. Astronomy and Astrophysics . 2020;642: A118.
Kierdorf, M., Mao, S. A., Beck, R., Basu, A., Fletcher, A., Horellou, C., Tabatabaei, F., et al. (2020). The magnetized disk-halo transition region of M51. Astronomy and Astrophysics , 642, A118. doi:10.1051/0004-6361/202037847
Kierdorf, M., Mao, S. A., Beck, R., Basu, A., Fletcher, A., Horellou, C., Tabatabaei, F., Ott, J., and Haverkorn, M. (2020). The magnetized disk-halo transition region of M51. Astronomy and Astrophysics 642:A118.
Kierdorf, M., et al., 2020. The magnetized disk-halo transition region of M51. Astronomy and Astrophysics , 642: A118.
M. Kierdorf, et al., “The magnetized disk-halo transition region of M51”, Astronomy and Astrophysics , vol. 642, 2020, : A118.
Kierdorf, M., Mao, S.A., Beck, R., Basu, A., Fletcher, A., Horellou, C., Tabatabaei, F., Ott, J., Haverkorn, M.: The magnetized disk-halo transition region of M51. Astronomy and Astrophysics . 642, : A118 (2020).
Kierdorf, M., Mao, S. A., Beck, R., Basu, Aritra, Fletcher, A., Horellou, C., Tabatabaei, F., Ott, J., and Haverkorn, M. “The magnetized disk-halo transition region of M51”. Astronomy and Astrophysics 642 (2020): A118.

Export

Markieren/ Markierung löschen
Markierte Publikationen

Open Data PUB

Web of Science

Dieser Datensatz im Web of Science®

Suchen in

Google Scholar