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Discovery of new globular clusters in the Bulge

Technical requirements: J images down to a limiting magnitude of $J\sim23$ is a $5\times5$ square degrees field.

Only a fraction of the GGC population has been discovered. We lack information on the GGC population in the central part of the Galaxy and in the Galactic plane beyond the Galactic center. A complete sample of GGC, particularly of the GGC in the central part of the Galaxy, would give the ratio of bulge/halo GGCs, i.e. information on the fraction of gas left after the halo formation. Moreover, GGC in the inner part of the Galaxy would give a unique opportunity to study the stellar population in very metal rich environments, as we expect that the most metal rich clusters are those embedded in the inner Galactic regions.

Barbuy et al. (1998, A&A, 333, 117) have estimated that at least 15 GGCs should be present in a cone of 5 degrees, centered on the Galactic center, beyond the center itself. These objects should have (m-M)0>14. If the absorption is AV=28, as toward tha Galactic center, these objects would have (m-M)V>42. However, the absorption in J is $A_J\sim0.28A_V$, i.e. we expect a $(m-M)_J\geq22$. The brightest stars in a GGC have negative absolute magnitudes, and they are naturally more clumped toward the cluster center than the field stars. Moreover, as in the very central part of the Galaxy we expect mainly high concentration GGCs (Chernoff and Weinberg 1989, ApJ, 339, 904), which have central surface brightness ($\mu_0<1$magnitudes/square arcsec, Djorgovski 1993, ASPCS, 50, 373), a survey in J, down to Jlim=23 of the central few degrees of the Galaxy would give a unique opportunity of finding new GGCs.


next up previous contents
Next: Open Clusters Up: Stellar populations Previous: White Dwarf Cooling Sequence
Guido Buscema
1999-01-29