2011/06/05 by Lisa Harvey-Smith, L. Harvey-Smith, G. J. Madsen +3 · 1 citation
Physics and Astronomy · #Astrophysics #Astrophysics and Star Formation Studies #Earth's magnetic field #Electron density #Faraday effect #Field strength #Galaxies: Formation, Evolution, Phenomena #L-shell #Line-of-sight #Magnetic field #Physics #Plasma #Stellar, planetary, and galactic studies #astro-ph.GA
paper · pdf · doi:10.1088/0004-637x/736/2/83
Accepted to the Astrophysical Journal, June 4th 2011
arxiv created 2011/06/05 · openalex publication_date 2011/07/11 · arxiv updated 2015/05/28 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We present a study of the line-of-sight magnetic fields in five large-diameter Galactic H ii regions. Using the Faraday rotation of background polarized radio sources, as well as dust-corrected Hα surface brightness as a probe of electron density, we estimated the strength and orientation of the magnetic field along 93 individual sight lines through the H ii regions. Each of the H ii regions displayed a coherent magnetic field. The magnetic field strength (line-of-sight component) in the regions ranges from 2 to 6 μG, which is similar to the typical magnetic field strength in the diffuse interstellar medium. We investigated the relationship between magnetic field strength and electron density in the five H ii regions. The slope of magnetic field versus density in the low-density regime (0.8 cm −3 < n e <30 cm −3 ) is very slightly above zero. We also calculated the ratio of thermal to magnetic pressure, β th , for each data point, which fell in the range 1.01 < β th < 25. Finally, we studied the orientation of the magnetic field in the solar neighborhood ( d < 1.1 kpc) using our data from five H ii regions along with existing measurements of the line-of-sight magnetic field strength from polarized pulsars whose distances have been determined from their annual parallax. We identify a net direction for the magnetic field in the solar neighborhood, but find no evidence for a preferred vertical direction of the magnetic field above or below the Galactic plane.