Magnetic field strengths in photodissociation regions

Journal Article · Fri Jan 01 04:00:00 EST 2016 · Astrophysical Journal

DOI:https://doi.org/10.3847/0004-637X/816/1/22· OSTI ID:22882326

Balser, Dana S.; Roshi, D. Anish ^[1]; Jeyakumar, S. ^[2]; Bania, T. M. ^[3]; Montet, Benjamin T. ^[4]; Shitanishi, J. A. ^[5]

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1. National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States)
2. Departamento de Astronomía, Universidad de Guanajuato, AP 144, Guanajuato CP 36000 (Mexico)
3. Institute for Astrophysical Research, Department of Astronomy, Boston University, 725 Commonwealth Avenue, Boston MA 02215 (United States)
4. Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States)
5. Department of Physics and Astronomy, University of Southern California, Los Angeles, CA 90089 (United States)

We measure carbon radio recombination line (RRL) emission at 5.3 GHz toward four H ii regions with the Green Bank Telescope to determine the magnetic field strength in the photodissociation region (PDR) that surrounds the ionized gas. Roshi suggests that the non-thermal line widths of carbon RRLs from PDRs are predominantly due to magneto-hydrodynamic waves, thus allowing the magnetic field strength to be derived. We model the PDR with a simple geometry and perform the non-LTE radiative transfer of the carbon RRL emission to solve for the PDR physical properties. Using the PDR mass density from these models and the carbon RRL non-thermal line width we estimate total magnetic field strengths of B∼100--300 μG in W3 and NGC 6334A. Our results for W49 and NGC 6334D are less well constrained with total magnetic field strengths between B∼ 200--1000 μG. H i and OH Zeeman measurements of the line of sight magnetic field strength (B{sub los}), taken from the literature, are between a factor of ∼0.5--1 of the lower bound of our carbon RRL magnetic field strength estimates. Since |B{sub los}|⩽B, our results are consistent with the magnetic origin of the non-thermal component of carbon RRL widths.

• OSTI ID: 22882326
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 816; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United Kingdom
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
CARBON
DENSITY
DISSOCIATION
EMISSION
GHZ RANGE
H2 REGIONS
LINE WIDTHS
LTE
MAGNETIC FIELDS
MAGNETOHYDRODYNAMICS
MASS
PHOTOLYSIS
RECOMBINATION
TELESCOPES
ZEEMAN EFFECT