SCYON Abstract

Received on October 29 2002

On the central structure of M15

AuthorsHolger Baumgardt (1), Piet Hut (2), Junichiro Makino (3), Steve McMillan (4), Simon Portegies Zwart (5)
Affiliation(1) Dep. of Astronomy, University of Tokyo
(2) Institue of Advanced Study, Princeton
(3) Dep. of Astronomy, University of Tokyo
(4) Dep. of Physics, Drexel University, Philadelphia
(5) Astron. Institute 'Anton Pannekoek', Univ. of Amsterdam
Submitted toAstrophysical Journal
Contactholger@astron.s.u-tokyo.ac.jp
URLhttp://arXiv.org/abs/astro-ph/0210133
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Abstract

We present a detailed comparison between the latest observational data on the kinematical structure of the core of M15, obtained with the Hubble STIS and WFPC2 instruments, and the results of dynamical simulations carried out using the special-purpose GRAPE-6 computer. The observations imply the presence of a significant amount of dark matter in the cluster core. In our dynamical simulations, neutron stars and massive white dwarfs concentrate to the center through mass segregation, resulting in a sharp increase in M/L toward the center. While consistent with the presence of a central black hole, the Hubble data can also be explained by this central concentration of neutron stars and massive white dwarfs. The latter interpretation is more conservative, since such remnants result naturally from stellar evolution. However, runaway merging leading to the formation of a black hole may also occur for some range of initial conditions. We conclude that no central massive object is required to explain the observational data, although we cannot exclude such an object at the level of 10^3 solar masses.