======================================================================== 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. 12 Jun 11, 2001 Recently submitted papers: -------------------------- 1) BIMA Observations of Linear Polarization in Sagittarius A* at 112 GHz (Bower et al., ApJL) 2) The Supermassive Black Hole at the Galactic Center (Melia & Falcke, ARA&A) 3) The lives and deaths of star clusters near the Galactic center (Zwart et al., ApJ) ------------------------------------------------------------------------ Email : gbower@palan.berkeley.edu Title : BIMA Observations of Linear Polarization in Sagittarius A* at 112 GHz Author(s): Geoffrey C. Bower(1,2), Melvyn C.H. Wright(2), Heino Falcke(3), Donald C. Backer(2) Institute: (1) National Radio Astronomy Observatory, P.O. Box O, 1003 Lopezville, Socorro, NM 87801; gbower@nrao.edu (2) Astronomy Department \& Radio Astronomy Laboratory, University of California, Berkeley, CA 94720; gbower,mwright,dbacker@astro.berk eley.edu (3) Max Planck Institut fuer Radioastronomie, Auf dem Huegel 69, D 53121 Bonn Germany; hfalcke@mpifr-bonn.mpg.de Paper : ApJL, in press EPrint : astro-ph/0106146 Web : http://astron.berkeley.edu/~gbower/ Abstract: We report here BIMA array observations of linear polarization in Sagittarius A*, the compact radio source in the Galactic Center. These observations had a resolution of 20'' * 5'' oriented North-South. We do not detect linear or circular polarization at a level of 1.8% (1- sigma) at 112 GHz. This puts a new constraint on models that show a sharp change in linear polarization fraction at 100 GHz. ------------------------------------------------------------------------ Email : hfalcke@sun184.mpifr-bonn.mpg.de Title : The Supermassive Black Hole at the Galactic Center Author(s): Fulvio Melia(1), Heino Falcke(2) Institute: (1) Physics Department and Steward Observatory, The University of Arizona, Tucson, AZ 85721 (2) Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, Bonn D-53121, Germany Paper : ARA&A, Vol. 39, in press EPrint : astro-ph/0106162 (available on Tuesday, June 12, 2001) Web : http://www.aoc.nrao.edu/staff/hfalcke/publications.html#gcreview Abstract: The inner few parsecs at the Galactic Center have come under intense scrutiny in recent years, in part due to the exciting broad-band observations of this region, but also because of the growing interest from theorists motivated to study the physics of black hole accretion, magnetized gas dynamics and unusual star formation. The Galactic Center is now known to contain arguably the most compelling supermassive black hole candidate, weighing in at a little over 2.6 million suns. Its interaction with the nearby environment, comprised of clusters of evolved and young stars, a molecular dusty ring, ionized gas streamers, diffuse hot gas, and a hypernova remnant, is providing a wealth of accretion phenomenology and high-energy processes for detailed modeling. In this review, we summarize the latest observational results, and focus on the physical interpretation of the most intriguing object in this region - the compact radio source Sgr A*, thought to be the radiative manifestation of the supermassive black hole. ------------------------------------------------------------------------ Email : spz@space.mit.edu Title : The lives and deaths of star clusters near the Galactic center Author(s): Simon F. Portegies Zwart^1, Junichiro Makino^2, Stephen L. W. McMillan^3, Piet Hut^4 Institute: ^1 Massachusetts Institute of Technology, Cambridge, MA 0213 9, USA , ^2 Department of Astronomy, University of Tokyo, 7-3-1 Hongo , Bunkyo-ku,Tokyo 113-0033, Japan , ^3 Department of Physics, Drexel University, Philadelphia, PA 19104, USA , ^4 Institute for Advanced Study, Princeton, NJ 08540, USA Paper : ApJ, submitted EPrint : astro-ph/0102259 Abstract: We study the evolution and observability of young, compact star clusters near the Galactic center, such as the Arches and Quintuplet systems. The clusters are modeled by integrating the equations of motion of all stars while accounting for the internal evolution of the stars and binaries and the effect of the tidal field of the Galaxy. We find that clusters within 150 pc of the Galactic center dissolve within 55 Myr, but their projected densities drop below the background density in the direction of the Galactic center within only a few Myr, effectively making these clusters undetectable after that time. Detailed observations of the Arches cluster, when taken at face value, suggest that its mass function is unusually flat and that the cluster contains an overabundance of stars more massive than 20M_o. Our dynamical analysis, however, shows that the observed characteristics of the Arches cluster are consistent with a perfectly normal initial mass function. The observed anomalies are caused by a combination of observational selection effects and the dynamical evolution of the cluster. We calibrate the current parameters of the Arches cluster using a normal initial mass function and conclude that the cluster is more massive than 40000 M_o, has a half mass radius of about 0.35 pc, and is located between 50 and 90 pc from the Galactic center. ------------------------------------------------------------------------ (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 ========================================================================