Vol 21, No 5

Self-similar orbit-averaged Fokker-Planck equation for isotropic spherical dense clusters (iii) Application to Galactic globular clusters

Yuta Ito


Abstract Fitting parametric models to globular clusters’ structural profiles has been essential for the study of stellar dynamics. It provides their important structural parameters, such as the concentrations and core radii of the clusters. However, existing parametric models can apply only to non-collapsing-core clusters in the early relaxation-evolution stage. Hence, a single parametric model cannot provide globular clusters’ structural parameters in both the early and late evolution stages. We have recently found an accurate spectral solution for the self-similar orbit-averaged Fokker-Planck (OAFP) equation to model collapsingcore clusters at the late evolution stage. The present work establishes a new parametric model by combining the self-similar OAFP- and polytropic- models. Although it is a single-mass and isotropic model, the new model applies to at least fifty-five Galactic globular clusters with resolved cores in all the evolution stages. As a main result, we show the characteristics of the relaxation times against the concentrations of the clusters. We also affirm that the structures of low-concentration clusters are polytropic in the Milky Way.


Keywords (Galaxy:) globular clusters: general — Galaxy: kinematics and dynamics — methods: numerical

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