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Abstract: Evolution of the mass function MF and radial distribution RD of theGalactic globular cluster GC system is calculated using an advanced and arealistic Fokker-Planck FP model that considers dynamical friction,disc-bulge shocks and eccentric cluster orbits. We perform hundreds of FPcalculations with different initial cluster conditions, and then search awide-parameter space for the best-fitting initial GC MF and RD that evolvesinto the observed present-day Galactic GC MF and RD. By allowing both MF and RDof the initial GC system to vary, which is attempted for the first time in thepresent Letter, we find that our best-fitting models have a higher peak massfor a lognormal initial MF and a higher cut-off mass for a power-law initial MFthan previous estimates, but our initial total masses in GCs, M {T,i} =1.5-1.8x10^8 Msun, are comparable to previous results. Significant findingsinclude that our best-fitting lognormal MF shifts downward by 0.35 dex duringthe period of 13 Gyr, and that our power-law initial MF models well-fit theobserved MF and RD only when the initial MF is truncated at >~10^5 Msun. Wealso find that our results are insensitive to the initial distribution of orbiteccentricity and inclination, but are rather sensitive to the initialconcentration of the clusters and to how the initial tidal radius is defined.If the clusters are assumed to be formed at the apocentre while filling thetidal radius there, M {T,i} can be as high as 6.9x10^8 Msun, which amounts to~75 per cent of the current mass in the stellar halo.



Autor: Jihye Shin, Sungsoo S. Kim, Koji Takahashi

Fuente: https://arxiv.org/







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