Extremely Large Telescope

Abstract:

We report the first results of an extensive new study of the Galactic center stellar cluster. The central parsec is powered by a cluster of about two dozen luminous and helium-rich blue supergiants/Wolf-Rayet stars (Teff i 20,000-30,000 K) with ZAMS masses up to -100 MQ. The most likely scenario for the formation of the massive stars is a small star formation burst between 3 X 106 and 7 X 106 years ago. In this scenario the Galactic center is presently in a short-lived, post-main-sequence “wind phase.” In addition, there is evidence for another star formation event about 108 years ago, as well as for recently formed massive stars that may have been transported into the central core along with orbiting gas streamers. The radial velocity dispersion of 35 early- and late-type stars with distances of 1"-12" from Sgr A* is 154 ± 19 km s-1. Our new results strongly favor the existence of a central dark mass of -3 X 106 M⊙ (density > 108.5 M⊙ pc-3, M/L > 10 M⊙/L⊙) within 0.14 pc of the dynamic center. © 1995 The American Astronomical Society.

Abstract:

We apply a new statistics, the factorial moment correlators, to density maps obtained from the APM survey The resulting correlators are all proportional to the two-point correlation function, substantially amplified with an amplification nearly exponential with the total rank of the correlators. This confirms the validity of the hierarchical clustering assumption on the dynamic range examined, corresponding to 0.5-50 h-1 Mpc in three-dimensional space. The Kirkwood superposition with loop terms is strongly rejected. The structure coefficients of the hierarchy are also fitted. The high quality of the APM catalog enabled us to disentangle the various contributions from the power spectrum, small-scale nonlinear clustering, and combinatorial effects, all of which affect the amplification of the correlators. These effects should appear in correlations of clusters in a similar fashion.