2020/07/15 by Yik Ki, Yik Ki Ma, S. A. Mao +4 · 24 citations
Physics and Astronomy · #Astronomy #Astrophysics #Astrophysics and Cosmic Phenomena #Disc #Galactic Center #Galactic plane #Galaxies: Formation, Evolution, Phenomena #Galaxy #Galaxy formation and evolution #Magnetic field #Milky Way #Physics #Pulsar #Radio Astronomy Observations and Technology #Spiral galaxy #astro-ph.GA
paper · pdf · doi:10.1093/mnras/staa2105
published in Monthly Notices of the Royal Astronomical Society 497(3), 3097-3117 (Oxford University Press) · 21 pages main text + 23 pages supplement; MNRAS accepted
arxiv created 2020/07/15 · openalex publication_date 2020/07/16 · openalex created_date 2020/07/23 · arxiv updated 2020/07/29 · openalex updated_date 2026/08/08
ABSTRACT The Milky Way is one of the very few spiral galaxies known to host large-scale magnetic field reversals. The existence of the field reversal in the first Galactic quadrant near the Sagittarius spiral arm has been well established, yet poorly characterized due to the insufficient number of reliable Faraday depths (FDs) from extragalactic radio sources (EGSs) through this reversal region. We have therefore performed broad-band (1–2 \rm GHz) spectropolarimetric observations with the Karl G. Jansky Very Large Array (VLA) to determine the FD values of 194 EGSs in the Galactic longitude range of 20°–52° within ±5° from the Galactic mid-plane, covering the Sagittarius arm tangent. This factor of five increase in the EGS FD density has led to the discovery of a disparity in FD values across the Galactic mid-plane in the Galactic longitude range of 40°–52°. Combined with existing pulsar FD measurements, we suggest that the Sagittarius arm can host an odd-parity disc field. We further compared our newly derived EGS FDs with the predictions of three major Galactic magnetic field models, and concluded that none of them can adequately reproduce our observational results. This has led to our development of new, improved models of the Milky Way disc magnetic field that will serve as an important step towards major future improvements in Galactic magnetic field models.