Department

Physics

Document Type

Article

Publication Date

5-2005

Embargo Period

8-31-2017

Abstract

New low-frequency 74 and 330 MHz observations of the Galactic center (GC) region reveal the presence of a large-scale (6° × 2°) diffuse source of nonthermal synchrotron emission. A minimum-energy analysis of this emission yields a total energy of ~(4/7f3/7) × 1052 ergs and a magnetic field strength of ~6(/f)2/7 μG (where is the proton to electron energy ratio and f is the filling factor of the synchrotron emitting gas). The equipartition particle energy density is 1.2(/f)2/7 eV cm-3, a value consistent with cosmic-ray data. However, the derived magnetic field is several orders of magnitude below the 1 mG field commonly invoked for the GC. With this field the source can be maintained with the supernova rate inferred from the GC star formation. Furthermore, a strong magnetic field implies an abnormally low GC cosmic-ray energy density. We conclude that the mean magnetic field in the GC region must be weak, of order 10 μG (at least on size scales 125'').

Journal

The Astrophysical Journal Letters

Journal ISSN

2041-8205

Volume

626

Issue

1

First Page

L23

Last Page

L27

Digital Object Identifier (DOI)

10.1086/431647

Included in

Physics Commons

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