======================================================================== 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. 13 Jun 27, 2001 Recently submitted papers: -------------------------- 1) The Stellar Winds of Galactic Centre and the Low Accretion Rate of Sgr A* (Coker, A&AL) 2) High Spectral and Spatial Resolution Observations of Shocked Molecular Hydrogen at the Galactic Center (Yusef-Zadeh et al., ApJ) ------------------------------------------------------------------------ Email : robc@ast.leeds.ac.uk Title : The Stellar Winds of Galactic Centre and the Low Accretion Rate of Sgr A* Author(s): R.F. Coker Paper : A&A Letters, in press EPrint : astro-ph/0106333 Abstract: An attempt is made to reconcile the large wind-loss rates of stars in the Galactic Centre (GC) with the predicted low accretion rate for Sgr A*, the putative blackhole at the heart of the Milky Way. It is found that, independent of the details of the accretion, the bound but unaccreted gas has been accumulating in the potential well of Sgr A* for less than 1000 yrs and thus is not in equilibrium. Otherwise, the gas flows of the region would be visible in both the IR and X-ray. It appears that the blackhole was more active in the recent past due to the passing of a supernova blast shock but is presently in a short-lived dormant phase. The extended low frequency radio emission from the central parsec should visibily increase over the next few decades, as the shock passes completely in front of the absorbing gas and dust near Sgr A*. The GC may become more active in less than 10,000 yrs due to either another supernova or sufficient accumulation of stellar winds in the central arcsecond. ------------------------------------------------------------------------ Email : zadeh@oort.astro.nwu.edu Title : High Spectral and Spatial Resolution Observations of Shocked Molecular Hydrogen at the Galactic Center Author(s): F. Yusef-Zadeh, S. R. Stolovy, M. Burton, M. Wardle, and M.C.B. Ashley Paper : ApJ, in press EPrint : astro-ph/0106190 Abstract: The presence of OH (1720 MHz) masers, and the absence of counterparts at 1665/1667 MHz has proved to be a clear diagnostic of shocked molecular gas associated with Galactic supernova remnants. This suggests that shocked molecular gas should be associated with the OH (1720 MHz) masers that have been detected in the circumnuclear disk (CND) and Sgr A East at the Galactic center. In order to test this hypothesis, we observed the H_2 1-0 S(1) and Br gamma lines using NICMOS on the HST and UNSWIRF on the AAT, near the regions where OH (1720 MHz) masers are detected in the CND and Sgr A East. We present the distribution of H_2 in the North and South lobes of the CND and in Sgr A East. H_2 emission accompanies almost all of the maser spots detected at the Galactic center. In particular, we find a striking filamentary structure near the Northwest of the CND and evidence that shocked molecular gas is associated with the 70 km/sec molecular cloud at the Galactic center. We argue that the emission from the CND could arise in gas heated by the dissipation of the random motion of clumps by collisions or the dissipation of turbulence in a more homogeneous medium. In addition, highly red-shifted gas of up to 140 km/sec close to the eastern edge of the Sgr A East shell is detected. These observations combined with OH (1720 MHz) results suggest that the H_2 gas is shocked and accelerated by the expansion of Sgr A East into the 50 and the 70 km/sec cloud and into the lobes of the CND. ------------------------------------------------------------------------ (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 ========================================================================