A Chandra View of Diffuse X-ray Emission in the Central 20 Parsecs of the Galaxy

Sangwook Park1, Frederick K. Baganoff2, Mark W. Bautz2, Gordon P. Garmire1, Yoshitomo Maeda1,3, Mark Morris4, and Michael P. Muno2

1 Department of Astronomy and Astrophysics, Penn State University, 525 Davey Lab., University Park, PA. 16802
2 Center for Space Research, MIT, Cambridge, MA. 02139
3 Institute of Space and Astronautical Science, 3-1-1 Yoshinodai, Sagamihara, Kanagawa, 229-8510, Japan
4 Department of Physics and Astronomy, UCLA, Los Angeles, CA. 90095

E-mail contact: park@astro.psu.edu

Over the last three years, the Galactic center region has been monitored with a series of the Chandra/ACIS observations. Besides the target object Sgr A*, the massive Galactic black hole candidate, the surrounding diffuse X-ray emission has been detected within the 17' x 17' ACIS field of view. As of 2002 June, combining all 11 GTO and GO observations, the total effective exposure reaches 590 ks, which reveals the detail structure of the faint filamentary diffuse X-ray emission with significant photon statistics. We here present some early results from the imaging/spectral analyses of these data. The ``true-color'' X-ray images of the Galactic center region indicate that the filamentary and diffuse X-ray emission features have complex spatio-spectral structures represented by various atomic line emission as well as hard continuum. We construct the equivalent width (EW) images for the detected elemental species Si, S, Ar, Ca, and Fe in order to map the distributions of these atomic emission lines in the vicinity of the Galactic center. We detect strong enhancements of He-like Fe within the 1.3' diameter circular region in the immediate east of Sgr A*. This is most likely emission from the highly ionized Fe associated with the recently identified supernova remnant (SNR) Sgr A East. A large-scale enhancement of the neutral Fe EW in the north-east of Sgr A* is in general spatially coincident with the molecular cloud M-0.02-0.07, which may support the X-ray reflection nebulae interpretation for the neutral Fe line emission in the Galactic center. The color images also reveal several shell-like emission features in various angular scales. X-ray emission from these individual filamentary structures show a variety of spectral characteristics from line-dominated to smooth continuum-like spectrum. These features may represent a population of young SNRs or stellar wind-blown bubbles around the Galactic center.