CHANG-ES. XV. Large-scale magnetic field reversals in the radio halo of NGC 4631 - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Astronomy and Astrophysics - A&A Année : 2019

CHANG-ES. XV. Large-scale magnetic field reversals in the radio halo of NGC 4631

Marita Krause
  • Fonction : Auteur
Aritra Basu
  • Fonction : Auteur
Rainer Beck
  • Fonction : Auteur
Theresa Wiegert
  • Fonction : Auteur
Judith Irwin
Richard Henriksen
  • Fonction : Auteur
Carlos Vargas
  • Fonction : Auteur
Volker Heesen
  • Fonction : Auteur
René Walterbos
  • Fonction : Auteur
Richard Rand
  • Fonction : Auteur
George Heald
  • Fonction : Auteur
Jiangtao Li
  • Fonction : Auteur
Patrick Kamieneski
  • Fonction : Auteur
Jayanne English
  • Fonction : Auteur

Résumé

Aims: NGC 4631 is an interacting galaxy which exhibits one of the largest gaseous halos observed among edge-on galaxies. We aim to examine the synchrotron and polarization properties of its disk and halo emission with new radio continuum data. Methods: Radio continuum observations of NGC 4631 were performed with the Karl G. Jansky Very Large Array at C-band (5.99 GHz) in the C and D array configurations, and at L-band (1.57 GHz) in the B, C, and D array configurations. The Rotation Measure Synthesis algorithm was utilized to derive the polarization properties. Results: We detected linearly polarized emission at C-band and L-band. The magnetic field in the halo is characterized by strong vertical components above and below the central region of the galaxy. The magnetic field in the disk is only clearly seen in the eastern side of NGC 4631, where it is parallel to the plane of the major axis of the galaxy. We detected for the first time a large-scale, smooth Faraday depth pattern in a halo of an external spiral galaxy, which implies the existence of a regular (coherent) magnetic field. A quasi-periodic pattern in Faraday depth with field reversals was found in the northern halo of the galaxy. Conclusions: The field reversals in the northern halo of NGC 4631, together with the observed polarization angles, indicate giant magnetic ropes with alternating directions. To our knowledge, this is the first time such reversals are observed in an external galaxy. Reduced polarized intensity images are also available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/632/A11
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Dates et versions

hal-03160336 , version 1 (21-05-2021)

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Silvia Carolina Mora-Partiarroyo, Marita Krause, Aritra Basu, Rainer Beck, Theresa Wiegert, et al.. CHANG-ES. XV. Large-scale magnetic field reversals in the radio halo of NGC 4631. Astronomy and Astrophysics - A&A, 2019, 632, pp.A11. ⟨10.1051/0004-6361/201935961⟩. ⟨hal-03160336⟩
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