Department
Physics
Document Type
Article
Publication Date
6-2005
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 ~(phi4/7f3/7) × 1052 ergs and a magnetic field strength of ~6(phi/f)2/7 μG (where phi 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(phi/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 gtrsim125'').
Journal Title
The Astrophysical Journal Letters
Journal ISSN
2041-8205
Volume
626
Issue
2
Digital Object Identifier (DOI)
10.1086/431647