HII Region Driven Galactic Bubbles and Their Relationship to the Galactic Magnetic Field

Abstract

The relative alignments of mid-infrared traced Galactic bubbles are compared to the orientation of the mean Galactic magnetic field in the disk. The orientations of bubbles in the northern Galactic plane were measured and are consistent with random orientations - no preferential alignment with respect to the Galactic disk was found. A subsample of HII region driven Galactic bubbles was identified, and as a single population they show random orientations. When this subsample was further divided into subthermal and suprathermal HII regions, based on hydrogren radio recombination linewidths, the subthermal HII regions showed a marginal deviation from random orientations, but the suprathermal HII regions showed significant alignment with the Galactic plane. The mean orientation of the Galactic disk magnetic field was characterized using new near-infrared starlight polarimetry and the suprathermal HII regions were found to preferentially align with the disk magnetic field. If suprathermal linewidths are associated with younger HII regions, then the evolution of young HII regions is significantly affected by the Galactic magnetic field. As HII regions age, they cease to be strongly linked to the Galactic magnetic field, as surrounding density variations come to dominate their morphological evolution. From the new observations, the ratios of magnetic-to-ram pressures in the expanding ionization fronts were estimated for younger HII regions.

12 pages, 7 figues, 3 tables; Accepted for publication in ApJ

References in corpus (13)

• The VLA Galactic Plane Survey
• The Dynamics of Radiation Pressure-Dominated HII Regions
• GREAT: the SOFIA high-frequency heterodyne instrument
• The Early Evolution of Massive Stars: Radio Recombination Line Spectra
• Full-Polarization Observations of OH Masers in Massive Star-Forming Regions: II. Maser Properties and the Interpretation of Polarization
• The Chemical Evolution of Helium
• The Green Bank Telescope HII Region Discovery Survey: III. Kinematic Distances
• A new probe of magnetic fields during high-mass star formation: Zeeman splitting of 6.7 GHz methanol masers
• Observational constraints on models for the interstellar magnetic field in the Galactic disk
• Magnetic fields in planetary nebulae and post-AGB nebulae
• MAGMO: Coherent magnetic fields in the star forming regions of the Carina-Sagittarius spiral arm tangent
• Magnetic Field Structure from Synchrotron Polarization
• HI Absorption Toward HII Regions at Small Galactic Longitudes

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