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Mass segregation in globular clusters

Technical requirements: V, I images down to a limiting magnitude of $V\sim27.5$ ( $I\sim 25.5$) in a $1\times1$ square degrees field.

For the same clusters observed for the tidal tails (but, of course, also other clusters independently observed), a large field imager would give the unique opportunity (in combination with already existing HST data for the central parts) to observationally map the mass segregation effect in the mass interval $0.15<m/m_\odot<0.8$ (or to smaller masses for clusters closer than m-M=15.5). Mass segregation tends to redistribute the stars of different masses at different radial distances from the cluster center. Presently, the MFs observed in small regions must be corrected with theoretical models in order to have the global MF of the cluster. Question are raised on the capability of theoretical models to correctly account for the mass segregation effects, particularly in those clusters which are undergone through strong dynamical evolution, such as core collapse clusters (Djorgovski and King 1984, 1986).

Again, we need to map the entire cluster plus an external region for the field contamination. The numbers are as in Section 1.1. Indeed, this project might be considered as complementary to the project outlined in Section 1.1. The combination of this project with the project describe above (and, in part, with the project outlined in the following section) would give us for the first time the opportunity to map the dynamical evolution of a sample of globular clusters both internal and externally induced by the interaction with the Galactic gravitational potential.

These data are essential to gather information on the initial mass function (IMF) of globular cluster stars, which indeed is what we are trying to get. Only the initial mass function can tell us how globular clusters have been formed. Because of the modifications on the mass function induced by the dynamical evolution, is not clear yet if a unique IMF applies to all the galactic globular clusters.


next up previous contents
Next: Study of the very Up: Stellar populations Previous: Mass Function of the
Guido Buscema
1999-01-29