======================================================================== G C N E W S * Newsflash * - The Newsletter for Galactic Center Research - gcnews@mpifr-bonn.mpg.de http://www.mpifr-bonn.mpg.de/gcnews ======================================================================== Vol. 13, No. 11 May 17, 2001 Recently submitted papers: -------------------------- 1) Chandra Observations of Diffuse X-Rays from the Sagittarius B2 Cloud (Murakami et al., ApJ) 2) ASCA Discovery of Diffuse 6.4 keV Emission Near the Sgr C Complex: A New X-ray Reflection Nebula (Murakami et al., ApJ) 3) NH_3 in the Central 10 pc of the Galaxy I: General Morphology and Kinematic Connections Between the CND and GMCs (McGary et al., ApJ) ------------------------------------------------------------------------ Email : hiro@cr.scphys.kyoto-u.ac.jp Title : Chandra Observations of Diffuse X-Rays from the Sagittarius B2 Cloud Author(s): Hiroshi Murakami(1), Katsuji Koyama(1), Yoshitomo Maeda(2,3) Institute: (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 (2) Department of Astronomy and Astrophysics, The Pennsylvania State University, 525 Davey Lab. University park, PA 16802; maeda@astro.psu.edu (3) Subaru Telescope, National Astronomical Observatory of Japan, 650 North Aohoku Place, Hilo, HI 96720 Paper : ApJ, accepted EPrint : astro-ph/0105273 Abstract: We present the first Chandra results of the giant molecular cloud Sagittarius B2 (Sgr B2), located about 100 pc away from the Galactic center. Diffuse X-rays are clearly separated from one-and-a-half dozen resolved point sources. The X-ray spectrum exhibits pronounced iron K-shell transition lines at 6.40 keV (K alpha ) and 7.06 keV (K beta ), deep iron K-edge at 7.11 keV and large photo-electric absorption at low energy. The absorption-corrected X-ray luminosity is 1*10^35 erg s^-1, two orders of magnitude larger than the integrated luminosity of all the resolved point sources. The diffuse X-rays come mainly from the south-west half of the cloud with a concave-shape pointing to the Galactic center direction. These results strongly support the ASCA model that Sgr B2 is irradiated by an X-ray source at the Galactic center side. ------------------------------------------------------------------------ Email : hiro@cr.scphys.kyoto-u.ac.jp Title : ASCA Discovery of Diffuse 6.4 keV Emission Near the Sgr C Complex: A New X-ray Reflection Nebula Author(s): Hiroshi Murakami(1,4), Katsuji Koyama(1,5), Masahiro Tsujimoto(1,4), Yoshitomo Maeda(2), Masaaki Sakano(3) Institute: (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, 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) Space Utilization Research Program, National Space Development Agency of Japan, 2-1-1, Sengen, Tsukuba, Ibaraki, 305-8505, Japan; sakano.masaaki@nasda.go.jp (4) Research Fellow of the Japan Society for the Promotion of Science (JSPS) (5) CREST, Japan Science and Technology Corporation (JST), 4-1-8 Honmachi, Kawaguchi, Saitama, 332-0012, Japan Paper : ApJ, 550, 297 (2001) EPrint : astro-ph/0012310 Abstract: We present an ASCA discovery of diffuse hard X-ray emission from the Sgr C complex with its peak in the vicinity of the molecular cloud core. The X-ray spectrum is characterized by a strong 6.4-keV line and large absorption. These properties suggest that Sgr C is a new X-ray reflection nebula which emits fluorescent and scattered X-rays via irradiation from an external X-ray source. We found no adequately bright source in the immediate Sgr C vicinity to fully account for the fluorescence. The irradiating source may be the Galactic nucleus Sgr A^*, which was brighter in the past than it is now as is suggested from observations of the first X-ray reflection nebula Sgr B2. ------------------------------------------------------------------------ Email : rmcgary@iorek.harvard.edu Title : NH_3 in the Central 10 pc of the Galaxy I: General Morphology and Kinematic Connections Between the CND and GMCs Author(s): Robeson S. McGary(1), Alison L. Coil(2), and Paul T.P. Ho(1) Institute: (1) Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138,,rmcgary@cfa.harvard.edu, pho@cfa.harvard.edu (2) Department of Astronomy, University of California, Berkeley, CA 94720, acoil@astro.berkeley.edu Paper : ApJ, 2001, in press EPrint : astro-ph/0105276 Abstract: New VLA images of NH_3 (1,1), (2,2), and (3,3) emission in the central 10 parsecs of the Galaxy trace filamentary streams of gas, several of which appear to feed the circumnuclear disk (CND). The NH_3 images have a spatial resolution of 16.5''*14.5'' and have better spatial sampling than previous NH_33 observations. The images show the ``southern streamer,'' ``50 km s^-1 cloud,'' and new features including a ``western streamer'', 6 parsecs in length, and a ``northern ridge'' which connects to the CND. NH_3(3,3) emission is very similar to 1.2 mm dust emission indicating that NH_3 traces column density well. Ratios of the NH_3(2,2) to (1,1) line intensities give an estimate of the temperature of the gas and indicate high temperatures close to the nucleus and CND. The new data cover a velocity range of 270 km s^-1, including all velocities observed in the CND, with a resolution of 9.8 km s^-1. Previous NH_3 observations with higher resolution did not cover the entire range of velocities seen in the CND. The large-scale kinematics of the CND do not resemble a coherent ring or disk. We see evidence for a high velocity cloud within a projected distance of 50'' (2 pc) which is only seen in NH_3(3,3) and is likely to be hot. Comparison to 6 cm continuum emission reveals that much of the NH_3 emission traces the outer edges of Sgr A East and was probably pushed outward by this expanding shell. The connection between the northern ridge (which appears to be swept up by Sgr A East) and the CND indicates that Sgr A East and the CND are in close proximity to each other. Kinematic evidence for these connections is presented in this paper, while the full kinematic analysis of the central 10 pc will be presented in Paper II. ------------------------------------------------------------------------ (Older versions of the Newsflash can be found at the gcnews web-page) ======================================================================== Edited by Angela Cotera Heino Falcke & Sera Markoff (cotera@as.arizona.edu) (hfalcke,smarkoff@mpifr-bonn.mpg.de) - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - For Abstract submission please send the (La)Tex file of your paper to gcnews@mpifr-bonn.mpg.de ========================================================================