ASCA Observations of the Sgr B2 Cloud:, An X-Ray Reflection Nebula
Hiroshi Murakami(1,3), Katsuji Koyama(1,4), Masaaki Sakano(1,3), and Masahiro Tsujimoto(1) Yoshitomo Maeda(2,3)
(1) Department of Physics, Faculty of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan; hiro@cr.scphys.kyoto-u.ac.jp, koyama@cr.scphys.kyoto-u.ac.jp, sakano@cr.scphys.kyoto-u.ac.jp, tsujimot@cr.scphys.kyoto-u.ac.jp
(2) Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802-6305, U.S.A.; maeda@astro.psu.edu
(3) Research Fellow of the Japan Society for the Promotion of Science (JSPS)
(4) CREST, Japan Science and Technology Corporation (JST), 4-1-8 Honmachi, Kawaguchi, Saitama, 332-0012, Japan
Paper: accepted in ApJ
Abstract:
We present the \ASCA results of imaging spectroscopy of the giant
molecular cloud Sgr B2. The X-ray spectrum is found to be very
peculiar; it exhibits a strong emission line at 6.4 keV, a low energy
cutoff below about 4 keV and a pronounced edge-structure at 7.1 keV. The
X-ray image is extended and its peak position is shifted from the core
of the molecular cloud toward the Galactic center by about 1-2
arcminute. The X-ray spectrum and the morphology are well reproduced
by a scenario that X-rays from an external source located in the
Galactic center direction are scattered by the molecular cloud Sgr B2,
and come into our line of sight. Thus Sgr B2 may be called an
X-ray reflection nebula. Possible implications of the Galactic center
activity related to this unique source are presented.
Preprints available from the authors at hiro@cr.scphys.kyoto-u.ac.jp
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