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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 720109.0, MPI für Astronomie / Publikationen_mpia
Properties of the magneto-ionic medium in the halo of M51 revealed by wide-band polarimetry
Authors:Mao, S. A.; Zweibel, E.; Fletcher, A.; Ott, J.; Tabatabaei, F.
Date of Publication (YYYY-MM-DD):2015
Title of Journal:The Astrophysical Journal
Issue / Number:2
Start Page:id. 92 (19 pp)
Audience:Not Specified
Abstract / Description:We present a study of the magneto-ionic medium in the Whirlpool galaxy (M51) using new wide-band multi-configuration polarization data at L band (1-2 GHz) obtained at the Karl G. Jansky Very Large Array. By fitting the observed diffuse complex polarization Q+iU as a function of wavelength directly to various depolarization models, we find that polarized emission from M51 at 1-2 GHz originates from the top of the synchrotron disk and then experiences Faraday rotation in the near-side thermal halo of the galaxy. Thus, the scale height of the thermal gas must exceed that of the synchrotron emitting gas at L band. The observed Faraday depth distribution at L band is consistent with a halo field that is comprised of a plane-parallel bisymmetric component and a vertical component that produces a Faraday rotation of ~-9 rad m-2. The derived rotation measure (RM) structure functions indicate a characteristic scale of RM fluctuations of less than 560 pc in the disk and approximately 1 kpc in the halo. The outer scale of turbulence of 1 kpc found in the halo of M51 is consistent with superbubbles and the Parker instability being the main energy injection mechanisms in galactic halos.
Free Keywords:Galaxy: halo; ISM: magnetic fields; polarization
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
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