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M. P. Muno, M. R. Morris (UCLA), F. K. Baganoff, M. W. Bautz, G. R. Ricker (MIT Center for Space Research), E. D. Feigelson, G. P. Garmire, S. Park, L. K. Townsely (PSU Department of Astrophysics)
We examine the spectrum of diffuse emission detected in the 17\arcmin\ by 17\arcmin\ field around Sgr A* during 625 ks of Chandra observations. The spectrum exhibits He-like and H-like lines from Si, S, Ar, Ca, and Fe, as well as a prominent low-ionization Fe line. The Si, S, and Ar lines can be modeled as a 0.8~keV plasma in thermal equilibrium. In contrast, the Fe emission between 6--7 keV could not be produced by a plasma this cool. Although the Fe emission is similar to that from the faint point sources in the field, arcminute-scale variations in the line equivalent widths indicate that unresolved point sources can produce at most 45% of the observed hard emission. Therefore, the Fe emission and associated hard continuum appears to be truly diffuse. The strengths and ratios of the He- and H-like Fe lines are consistent plasma component in thermal equilibrium with kT=8 keV. The pressure of this plasma is two orders of magnitude higher than that of the ISM in the Galactic plane, but it is comparable to (1) the turbulent pressure of the molecular clouds near the Galactic center, and (2) the magnetic pressure inferred for the observed radio filaments. These X-ray observations provide further evidence that the ISM in the Galactic center is maintained at a very high pressure, which has dramatic consequences for how stars can form there, and for the possible formation of a Galactic wind.
The author(s) of this abstract have provided an email address for comments about the abstract: mmuno@astro.ucla.edu
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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.