Subject: GCFLASH - Vol. 1, No. 6 (May 2, 1996) ======================================================================== G C N E W S * Newsflash * - The Newsletter for Galactic Center Research - gcnews@astro.umd.edu http://www.astro.umd.edu/~gcnews ======================================================================== Vol. 1, No. 6 May 2, 1996 Dear Subscribers, There will be only one more Newsflash before the premier issue of the Newsletter will be compiled and distributed. If you have any papers, announcements, posted job offers, or inquiries, you want to have included in this issue of GCNEWS please email us as soon as possible. We expect to finish the final version over the wnext days. For those of you who have UNIX machines, we will be distributing a little script that automatically extracts and prints a (any) PS file from your mailbox - so the Newsletter is only a few keystrokes away. Your GCNEWS Team Recently submitted papers: -------------------------- 1) The Molecular Gas in the Galactic Center Region based on C^18O Measurements, Presentation of a Large Scale J = 1 - 0 Survey obtained with the 1.2m Southern Millimeter-Wave Telescope at CTIO (Dahmen et al.) 2) KINEMATICS OF THE IONIZED GAS IN SGR A WEST: THE MINICAVITY AND THE WESTERN ARC (Roberts et al.) 3) Sgr A* and its siblings in nearby galaxies (Falcke) 4) H_2 Emission from the Inner 400 Parsecs of the Galaxy, II. The UV-Excited H_2 (Pak et al.) ------------------------------------------------------------------------ Email : G.Dahmen@qmw.ac.uk Title : The Molecular Gas in the Galactic Center Region based on C^18O Measurements, Presentation of a Large Scale J = 1 - 0 Survey obtained with the 1.2m Southern Millimeter-Wave Telescope at CTIO Author(s): G. Dahmen(1,2), S. Huettemeister(3,1), T.L. Wilson(1), R. Mauersberger(4,1), A. Linhart(1), L. Bronfman(5), A.R. Tieftrunk(1), K. Meyer(1), W. Wiedenhvver(1), T.M. Dame(3), E.S. Palmer(3), J. May(5), J. Aparici(5), F. Mac-Auliffe(5) Institute: (1) Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, 53121 Bonn, Germany (2) Physics Department, Queen Mary & Westfield College, University of London, Mile End Road, London E1 4NS, U.K. (3) Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, U.S.A. (4) Steward Observatory, The University of Arizona, Tucson, AZ 85716, U.S.A. (5) Departamento de Astronomma, Universidad de Chile, Casilla 36-D, Santiago de Chile, Chile Paper : to appear in the Proceedings of the 4th ESO/CTO Workshop "The Galactic Center", ASP Conf. Series, R. Gredel (ed.) Weblink : http://starsun7.ph.qmw.ac.uk/~dahmen/gdahmen.html Abstract: A large scale C^18O(J=1-0) survey of the central few hundred pc (-1.05^o <= l <= +3.6^o, -0.9^o <= b <= +0.75^o) of the Galaxy is presented. These 9^' resolution data were obtained with the 1.2 m Southern Millimeter-Wave Telescope (SMWT) at CTIO and compared to ^12CO(1-0) data also obtained with this telescope. In addition, HNCO(5_0,5-4_0,4) line data included in the spectrometer passband are also presented. Although both ^12CO and C^18O are thought to be tracers of the molecular mass, their distribution and line shapes differ significantly. The C^18O(1-0) line is mucher weaker than expected from the ``Standard I_^12CO(1-0)/N_H_2 Conversion Formula'' obtained by Strong et al. (1988). LVG calculations suggest that on large scales the ^12CO(1-0) emission is only of intermediate ( tau = 1 - 5) or low optical depth ( tau < 1). In this case, the ``Standard Conversion Formula'' overestimates N_H_2. Our C^18O(1-0) data combined with other H_2 tracers indicate a total molecular mass of (3^+2_-1) * 10^7 M_o. The existence of a widespread component of molecular gas with low density (thin gas) is found to be very likely. ------------------------------------------------------------------------ Email : droberts@lai.ncsa.uiuc.edu Title : KINEMATICS OF THE IONIZED GAS IN SGR A WEST: THE MINICAVITY AND THE WESTERN ARC Author(s): D.A. Roberts F. Yusef-Zadeh W.M. Goss Institute: (1) University of Illinois, NCSA, 405 N. Mathews Ave, Urbana, IL 61801 (2) Northwestern University, Department of Physics and Astronomy, Evanston, IL 60208 (3) NRAO, P.O. Box 0, Socorro, NM 87801 Paper : to appear in the 4th ESO/CTIO Workshop on the Galactic Center Proceedings Abstract: The ``western arc'' and ``minicavity''(approximately 3^'' southwest of Sgr A*) of the Galactic center H II region Sgr A West have been imaged in the H 92 alpha line at 8.3 GHz with the VLA. The kinematics of the ionized gas in the inner 1.5 parsecs of the Galactic center have been determined. The western arc, with an inner radius of 1 pc, appears to be in circular rotation about a point near Sgr A*, with an enclosed mass of ~ 3.5 * 10^6 M_o. Toward the minicavity, a large velocity gradient (> 600 km s^-1 pc^-1) is observed along the eastern rim and uniformly large velocities are observed along the western rim. The velocity field of the minicavity is interpreted as gas in a hyperbolic orbit about Sgr A*. Based on this model, the gas is orbiting a point at the position of Sgr A* with a mass of ~3.0 * 10^6 M_o. ------------------------------------------------------------------------ Email : hfalcke@astro.umd.edu Title : Sgr A* and its siblings in nearby galaxies Author(s): Heino Falcke Institute: Department of Astronomy, University of Maryland, College Park, MD 20742-2421, USA (hfalcke@astro.umd.edu) Paper : to appear in: Proc. of the 4th ESO/CTIO Workshop "The Galactic Center", ASP Conf. Series, R. Gredel (ed.) Weblink : http://www.astro.umd.edu/~hfalcke/publications.html#esogcpap EPrint : astro-ph/9604185 Abstract: We have proposed previously that Sgr A* is simply a scaled down AGN with a black hole, an accretion disk and a radio jet operating at a very low power. It appears as if M81* - the nuclear source in the nearby galaxy M81 - is an ideal laboratory to study a Sgr A*-like source at a higher power level. The jet/disk model can explain M81* in great detail with no basic changes in the model parameters other than the accretion rate. Radio cores in other LINERs may be explained by the same model and they appear to be low-power counterparts to radio-loud quasar cores. For Sgr A*, models without a supermassive black hole are facing difficulties - some of which are discussed here, but a persistent puzzle in any scenario are the non-detections and low flux limits for Sgr A* from IR to x-rays. Especially the IR limits are a threat to accretion models. I discuss whether a thin molecular disk (as seen in NGC 4258) around Sgr A* could intercept infalling material before it reaches the black hole. ------------------------------------------------------------------------ Email : soojong@astro.as.utexas.edu Title : H_2 Emission from the Inner 400 Parsecs of the Galaxy, II. The UV-Excited H_2 Author(s): Soojong Pak(1), D. T. Jaffe, and L. D. Keller(1) Institute: (1) Astronomy Department, University of Texas, Austin, TX 78712 (2) Visiting Astronomer, Cerro Tololo Inter-American Observatory, National Optical Astronomy Observtory, which are operated by the Association of Universities for Research in Astronomy, under contract with the National Science Foundation Paper : the 4th ESO/CTIO Workshop (see also ApJ 457, L43 (1996)) Eprint : astro-ph/9604173 (astro-ph/9604174 (ApJL)) Abstract: We have observed near-IR H_2 line emission on large scales in the Galactic center. Paper I discussed our 400 pc long strip map and 50 pc map of the H_2 v=1-> 0 S(1) line. In this paper, we present observations of the higher vibrational lines (H_2 v=2-> 1 S(1) and v=3-> 2 S(3)) at selected positions and conclude that strong far-UV radiations excites the H_2. We compare the H_2 v=1-> 0 S(1) emission to far-IR continuum emission and show that the ratio of these two quantities in the Galactic center equals the ratio seen in the starburst galaxies, M82 and NGC 253, and in ultraluminous infrared bright galaxies. ------------------------------------------------------------------------ (Older versions of the Newsflash can be found at the gcnews web-page) ======================================================================== Edited by Angela Cotera Heino Falcke (cotera@ipac.caltech.edu) (hfalcke@astro.umd.edu) - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - For Abstract submission please send the (La)Tex file of your paper to gcnews@astro.umd.edu ========================================================================