AAS 201st Meeting, January, 2003
Session 31. The Galactic Center and Its Environs
Oral, Monday, January 6, 2003, 2:00-3:30pm, 6AB

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[31.03] A New Insight into the Galactic Center Magnetic Field: Discovery of Nonthermal Filaments with Random Orientations

T.N. LaRosa (Kennesaw State College), M.E. Nord (Naval Research Laboratory / University of New Mexico), T.J.W. Lazio, N.E. Kassim (Naval Research Laboratory)

The isolated nonthermal filaments (NTFs) observed in the Galactic center are unique to that region. They are characterized by extreme length to width ratios (from ~10 to >100), strong polarization (30%-70%), strong magnetic fields (~1 mG) aligned along their long axis, and nonthermal spectra. The conventional view is that they trace a large-scale poloidal Galactic center magnetic field.

New high-resolution, 90 cm observations of the GC region made with the VLA reveal as many as a dozen previously unknown nonthermal filament (NTF) candidates with a variety of orientations. Follow up VLA observations of five of these sources at 6 cm indicates that all of these candidates have the expected NTF morphology and two show strong polarization.

One of these systems is located in the Sgr B region, north of the Galactic Center Radio Arc. These filaments cross the galactic plane and extend the volume over which the NTF phenomena is known to occur. The other polarized NTF was found south of Sgr C filament but with an orientation nearly parallel to the galactic plane. This is only the second of 11 confirmed NTFs that is not perpendicular to the galactic plane. Two additional candidates in Sgr C were resolved into filamentary systems although polarization was not detected at our sensitivity levels. These sources exhibit considerable curvature and are also largely parallel to the galactic plane.

We have therefore confirmed that NTFs in close proximity (in projection) to each other have very different directions. We conclude that the galactic center magnetic field is more complex than a simple globally ordered poloidal field. It is also possible that the NTFs maybe tracing independent local fields.

Basic research in radio astronomy at the Naval Research Laboratory is supported by the Office of Naval Research. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities,Inc.

The author(s) of this abstract have provided an email address for comments about the abstract: ted@avatar.kennesaw.edu

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