INITIAL SIZE DISTRIBUTION OF THE GALACTIC GLOBULAR CLUSTER SYSTEM

作者：Shin Jihye^*; Kim Sungsoo S; Yoon Suk Jin; Kim Juhan

来源：Astrophysical Journal, 2013, 762(2): 135.

DOI：10.1088/0004-637X/762/2/135

• Galaxy: evolution
• Galaxy: formation
• Galaxy: kinematics and dynamics
• globular clusters: general
• methods: numerical

Despite the importance of their size evolution in understanding the dynamical evolution of globular clusters (GCs) of the Milky Way, studies that focus specifically on this issue are rare. Based on the advanced, realistic Fokker-Planck (FP) approach, we theoretically predict the initial size distribution (SD) of the Galactic GCs along with their initial mass function and radial distribution. Over one thousand FP calculations in a wide parameter space have pinpointed the best-fit initial conditions for the SD, mass function, and radial distribution. Our best-fit model shows that the initial SD of the Galactic GCs is of larger dispersion than today%26apos;s SD, and that the typical projected half-light radius of the initial GCs is similar to 4.6 pc, which is 1.8 times larger than that of the present-day GCs (similar to 2.5 pc). Their large size signifies greater susceptibility to the Galactic tides: the total mass of destroyed GCs reaches 3-5 x 10(8) M-circle dot, several times larger than previous estimates. Our result challenges a recent view that the Milky Way GCs were born compact on the sub-pc scale, and rather implies that (1) the initial GCs were generally larger than the typical size of the present-day GCs, (2) the initially large GCs mostly shrank and/or disrupted as a result of the galactic tides, and (3) the initially small GCs expanded by two-body relaxation, and later shrank by the galactic tides.

• 出版日期2013-1-10