2014/12/29 by S. A. Mao, E. Zweibel, A. Fletcher +2 · 35 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics and Star Formation Studies #Faraday effect #Galactic halo #Galaxies: Formation, Evolution, Phenomena #Galaxy #Halo #Interstellar medium #Polarimetry #Polarization (electrochemistry) #Spiral galaxy #Synchrotron #Synchrotron radiation #astro-ph.GA
paper · pdf · doi:10.1088/0004-637x/800/2/92
published in The Astrophysical Journal 800(2), 92 (IOP Publishing) · 36 pages, 19 figures, 3 tables. Accepted for publication in ApJ
arxiv created 2014/12/29 · openalex publication_date 2015/02/17 · arxiv updated 2015/06/23 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/06
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.