======================================================================== G C N E W S * Newsflash * - The Newsletter for Galactic Center Research - gcnews@aoc.nrao.edu http://www.aoc.nrao.edu/~gcnews ======================================================================== Vol. 24, No. 6 May 19, 2006 Recently submitted papers: -------------------------- 1) Diffraction Limited Imaging Spectroscopy of the SgrA* Region using OSIRIS, a new Keck Instrument (Krabbe et al., ApJ) 2) Exploring High-Velocity NH3(6,6) Emission at the Center of our Galaxy (Donovan et al., ApJ) 3) ORGANIC MOLECULES IN THE GALACTIC CENTER; HOT CORE CHEMISTRY WITHOUT HOT CORES (Requena-Torres et al., A&A) ------------------------------------------------------------------------ Email : iserlohe@ph1.uni-koeln.de Title : Diffraction Limited Imaging Spectroscopy of the SgrA* Region using OSIRIS, a new Keck Instrument Author(s): A. Krabbe, C. Iserlohe J. E. Larkin, M. Barczys, M. McElwain, J. Weiss, S. A. Wright A. Quirrenbach Institute: (1) I. Physikalisches Institut, Universitaet zu Koeln, 50937 Koeln, Germany (2) Division of Astronomy, University of California, Los Angeles, CA, 90095-1562, USA (3) Leiden Observatory, P.O. Box 9513, NL-2300 RA Leiden, The Netherlands Paper : ApJ 2006, in press EPrint : astro-ph/0605253 Abstract: We present diffraction limited spectroscopic observations of an infrared flare associated with the radio source SgrA*. These are the first results obtained with OSIRIS, the new facility infrared imaging spectrograph for the Keck Observatory operated with the laser guide star adaptive optics system. After subtracting the spectrum of precursor emission at the location of Sgr A*, we find the flare has a spectral index (F( nu ) \propto nu ^ alpha ) of alpha = -2.6 +/- 0.9. If we do not subtract the precursor light, then our spectral index is consistent with earlier observations by Ghez et al. (2005). All observations published so far suggest that the spectral index is a function of the flare's K-band flux. ------------------------------------------------------------------------ Email : jen@astro.columbia.edu Title : Exploring High-Velocity NH3(6,6) Emission at the Center of our Galaxy Author(s): Jennifer L. Donovan^1, Robeson M. Herrnstein^1, and Paul T.P. Ho^2,3 Institute: (1) Department of Astronomy, Columbia University, 550 West 120th St., Mail Code 5246, New York, NY 10027 (2) Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 (3) Academia Sinica Institute of Astronomy and Astrophysics, Taipei Paper : ApJ, Aug 2006, accepted EPrint : astro-ph/0605280 Abstract: Using the NH3 (6,6) transition, which samples dense ( 10^5) molecular gas with an energy above ground of 412 K, we find hot gas at high velocities (-142 to -210 km s^-1) associated with the central 2 pc of the Galactic center. This material may be either infalling gas due to shocks or tidal stripping, or possibly gas swept from the nuclear region. We identify two high-velocity features, which we call the Southern Runner and the Cap, and correlate these features with others detected in various molecular observations of the Galactic center. The characteristic linewidths of the Southern Runner and Cap, 10 - 15 km/sec , are similar to those of other hot Galactic center clouds. The estimated H_2 masses of these clouds are 4* 10^3 M\sol and 2* 10^3 M\sol, consistent with the masses of the western streamer and northern ridge, NH3 (6,6) emission features detected within the central 10 pc at lower velocities. Three possible explanations for this emission are discussed assuming that they lie at the Galactic center, including sweeping by the supernova remnant Sgr A East, infall and/or shock from the circumnuclear disk (CND), and stripping from the central rotating low-velocity NH3 (6,6) cloud. ------------------------------------------------------------------------ Email : requena@damir.iem.csic.es Title : ORGANIC MOLECULES IN THE GALACTIC CENTER; HOT CORE CHEMISTRY WITHOUT HOT CORES Author(s): M. A. Requena-Torres(1), J. Martin-Pintado(1), A. Rodriguez-Franco, (1)(2) S. Martin(3), N. J. Rodriguez-Fernandez(4), and P. de Vicente(5) Institute: (1) Departamento de Astrofisica Molecular e Infrarroja, Instituto de Estructura de la Materia-CSIC C Serrano 121, E-28006 Madrid, Spain, (2) Escuela Universitaria de Optica, Departamento de Matematica Aplicada (Biomatematica), Universidad Complutense de Madrid, Avenida Arcos de Jalon s/n, E-28037 Madrid, Spain, (3) Instituto de Radioastronomia Milimetrica Av. Divina Pastora 7, Local 20, E-18012 Granada, Spain, (4) Observatoire de Bordeaux, L3AB (UMR 5804), CNRS/Universite Bordeaux 1, BP 89, 2 rue de l'Observatoire, 33270 Floirac, France, (5) Observatorio Astronomico Nacional, Centro Astronomico de Yebes Apartado 148, 19080 Guadalajara, Spain Paper : A&A accepted EPrint : astro-ph/0605031 Web : http://www.damir.iem.csic.es Abstract: We study the origin of large abundances of complex organic molecules in the Galactic center (GC). We carried out a systematic study of the complex organic molecules CH_3OH, C_2H_5OH, (CH_3)_2O, HCOOCH_3, HCOOH, CH_3COOH, H_2CO, and CS toward 40 GC molecular clouds. Using the LTE approximation, we derived the physical properties of GC molecular clouds and the abundances of the complex molecules. The CH_3OH abundance between clouds varies by nearly two orders of magnitude from 2.4*10^-8 to 1.1*10^-6. The abundance of the other complex organic molecules relative to that of CH_3OH is basically independent of the CH_3OH abundance, with variations of only a factor 4-8. The abundances of complex organic molecules in the GC are compared with those measured in hot cores and hot corinos, in which these complex molecules are also abundant. We find that both the abundance and the abundance ratios of the complex molecules relative to CH_3OH in hot cores are similar to those found in the GC clouds. However, hot corinos show different abundance ratios than observed in hot cores and in GC clouds. The rather constant abundance of all the complex molecules relative to CH_3OH suggests that all complex molecules are ejected from grain mantles by shocks. Frequent ( 10^5 years) shocks with velocities >6 km s^-1 are required to explain the high abundances in gas phase of complex organic molecules in the GC molecular clouds. The rather uniform abundance ratios in the GC clouds and in Galactic hot cores indicate a similar average composition of grain mantles in both kinds of regions. The Sickle and the Thermal Radio Arches, affected by UV radiation, show different relative abundances in the complex organic molecules due to the differentially photodissociation of these molecules. ------------------------------------------------------------------------ (Older versions of the Newsflash can be found at the gcnews web-page) ======================================================================== Edited by Sera Markoff, Loránt Sjouwerman, Joseph Lazio, Cornelia Lang, Rainer Schödel, Robin Herrnstein - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - For Abstract submission please follow the instructions which are at http://www.aoc.nrao.edu/~gcnews/home/submission.shtml ========================================================================