NGC 2419: An M92 Twin At 95 Kpc

Session 71 - Globular Clusters.
Display session, Wednesday, January 15
Metropolitan Ballroom,

[71.02] NGC 2419: An M92 Twin At 95 Kpc

J. E. Hesser, P. B. Stetson, R. D. McClure, S. van den Bergh (NRC/HIA/DAO), W. E. Harris (McMaster U.), M. Bolte (Lick), D. A. VandenBerg (U. Victoria), H. E. Bond (STScI), G. G. Fahlman, H. B. Richer (UBC), R. A. Bell (U. Md.)

Cycle 4 amp; 5 data from WFPC2 on HST have been reduced with ALLFRAME to produce a V (F555W) and I (F814W) color-magnitude diagram (CMD) for NGC 2419 that reaches M_v \sim +8. This populous globular cluster in the far Galactic halo has [Fe/H] =-2.1, which is virtually identical to that of NGC 6341 (M92) at R_gc=10 kpc. In superposition, the CMDs for these two clusters are virtually indistinguishable. Such similarity suggests that a global star cluster formation event occurred over a huge volume in the protogalaxy, providing that the present separation reflects the initial one (which other evidence substantiates). The fact that all the most metal-deficient globular clusters with accurate CMDs exhibit the same ages to within \sim0.5 Gyr stringently constrains Galactic formation scenarios.

Program listing for Wednesday