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Symmetries and dynamics of star clusters
Haas, Jaroslav ; Šubr, Ladislav (advisor) ; Baumgardt, Holger (referee) ; Jungwiert, Bruno (referee)
We investigate the orbital evolution of an initially thin stellar disc around a supermassive black hole, considering various perturbative sources of gravity. By means of direct numerical N-body modelling, we first focus on the case when the disc is embedded in an extended spherically symmetric star cluster. We find that the gravitational influence of the disc triggers formation of macroscopic non- spherical substructure in the cluster which, subsequently, significantly affects the evolution of the disc itself. In another approximation, when the cluster is emu- lated by an analytic spherically symmetric potential, we further consider pertur- bative gravitational influence of a distant axisymmetric source. Using standard perturbation methods, we derive a simple semi-analytic model for such a config- uration. It turns out that the additional axisymmetric potential leads to mutual gravitational coupling of the individual orbits from the disc. Consequently, the dense parts of the disc can, for some period of time, evolve coherently. Finally, we apply some of our results to the young stellar disc which is observed in the innermost parsec of the Galactic Centre. 1
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Symmetries and dynamics of star clusters
Haas, Jaroslav
We investigate the orbital evolution of an initially thin stellar disc around a supermassive black hole, considering various perturbative sources of gravity. By means of direct numerical N-body modelling, we first focus on the case when the disc is embedded in an extended spherically symmetric star cluster. We find that the gravitational influence of the disc triggers formation of macroscopic non- spherical substructure in the cluster which, subsequently, significantly affects the evolution of the disc itself. In another approximation, when the cluster is emu- lated by an analytic spherically symmetric potential, we further consider pertur- bative gravitational influence of a distant axisymmetric source. Using standard perturbation methods, we derive a simple semi-analytic model for such a config- uration. It turns out that the additional axisymmetric potential leads to mutual gravitational coupling of the individual orbits from the disc. Consequently, the dense parts of the disc can, for some period of time, evolve coherently. Finally, we apply some of our results to the young stellar disc which is observed in the innermost parsec of the Galactic Centre. 1
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Dynamics of young stars in the Galactic nucleus
Haas, Jaroslav ; Šubr, Ladislav (advisor) ; Mayer, Pavel (referee)
As observations show, there are two coherently rotating structures of a few tens of young stars in the centre of our Galaxy close to a supermassive black hole. One of them contains a very dense star cluster, so-called complex IRS 13E. There are some speculations there might be an intermediate mass black hole with mass of the order of 103 -104 M in its centre. Using numerical simulations of the stellar dynamics in the dominant potential of Sgr A* disturbed by IRS 13E and a spherically symmetric cluster of old stars, which is believed to be there too, I have set upper limits on the masses of both disturbers, which guarantee, that the disturbers' presence cannot be of a destructive inuence on observed conguration of the system. It comes out that the incidence of the spherically symmetric star cluster is very stabilizing. My results show that the upper mass limit of the IRS 13E can be an order of magnitude higher, when the spherical cluster is considered (6 × 104 M) in comparison to the case, when it is omitted (4,5 × 103 M).
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