======================================================================== 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. 10, No. 3 Jun 17, 1999 Recently submitted papers: -------------------------- Email : figer@astro.ucla.edu Title : HST/NICMOS Observations of Massive Stellar Clusters Near the Galactic Center Author(s): Donald F. Figer(1,2), Sungsoo S. Kim(1,3), Mark Morris(1), Eugene Serabyn(4), R. Michael Rich(1), Ian S. McLean(1) Institute: (1) University of California, Los Angeles, Division of Astronomy, Department of Physics \& Astronomy, Los Angeles, CA, 90095-1562; figer@astro.ucla.edu, sskim@astro.ucla.edu, morris@astro.ucla.edu, rmr@astro.ucla.edu (2) Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (3) Korea Advanced Institute of Science and Technology, Department of Physics, Space Science Laboratory, Daejon, 305-701, Korea (4) JPL 171-113, 4800 Oak Grove Dr., Pasadena, CA 91109; eserabyn@huey.jpl.nasa.gov Paper : ApJ, accepted Weblink : http://www.astro.ucla.edu/~figer/papers.html Abstract: We report Hubble Space Telescope (HST) Near-infrared Camera and Multi-object Spectrometer (NICMOS) observations of the Arches and Quintuplet clusters, two extraordinary young clusters near the Galactic Center. For the first time, we have identified main sequence stars in the Galactic Center with initial masses well below 10 M_sun. We present the first determination of the initial mass function (IMF) for any population in the Galactic Center, finding an IMF slope which is significantly more positive (Gamma ~ -0.65) than the average for young clusters elsewhere in the Galaxy (Gamma ~ -1.4). The apparent turnoffs in the color-magnitude diagrams suggest cluster ages which are consistent with the ages implied by the mixture of spectral types in the clusters; we find tau _age ~ 2+/-1 Myr for the Arches cluster, and tau _age ~ 4+/-1 Myr for the Quintuplet. We estimate total cluster masses by adding the masses of observed stars down to the 50% completeness limit, and then extrapolating down to a lower mass cutoff of 1 M_sun. Using this method, we find >~10^4 M_sun for the total mass of the Arches cluster. Such a determination for the Quintuplet cluster is complicated by the double-valued mass-magnitude relationship for clusters with ages >~ 3 Myr. We find a lower limit of 6300 M_sun for the total cluster mass, and suggest a best estimate of twice this value which accounts for the outlying members of the cluster. Both clusters have masses which place them as the two most massive clusters in the Galaxy. ------------------------------------------------------------------------ (Older versions of the Newsflash can be found at the gcnews web-page) ======================================================================== Edited by Angela Cotera Heino Falcke (cotera@ipac.caltech.edu) (hfalcke@mpifr-bonn.mpg.de) - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - For Abstract submission please send the (La)Tex file of your paper to gcnews@mpifr-bonn.mpg.de ========================================================================