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The influence of the stellar mass-loss on the dynamics of star clusters
Dinnbier, František ; Jungwiert, Bruno (advisor) ; Šubr, Ladislav (referee)
This work aims at studying the influence of the stellar mass-loss, resulting from the stellar evolution, on the dynamics of massive star clusters. The emphasis has been put on the mass-loss by low-mass and intermediate-mass stars (m < 8 Mo) that form, at the end of their life, a planetary nebula. The expansion speed of gas released by these stars is lower than the escape speed from sufficiently massive star clusters, and the gas can be retained by the cluster. For modelling of the gas hydrodynamics, a simple sticky-particles method was used. To carry out simulations in which gaseous and stellar particles mutually interact through their gravity, substantial modifications had to be realized in the N-body codes Nbody6 and Hermit. For the sake of comparing the influence of stellar mass-loss and relaxation processes, which are happening in the simplified model, two types of simulations were performed: one with the formation of gaseous particles and the other consisting of purely stellar component. The simulations in which the gas component was present showed out a significantly different evolution in the central part of the cluster than those in which the presence of gas was not considered.
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Perturbed stellar motion in dense star clusters
Pavlík, Václav ; Šubr, Ladislav (advisor) ; Davies, B. Melvyn (referee) ; Portegies Zwart, Simon (referee)
Star clusters are thought to be the birthplaces of stars as well as the building blocks of galaxies. They typically consist of thousands to millions of stars bound together by self-gravity. These systems evolve on the scale of Myr to Gyr, there- fore, it is impossible for us to see any change in their global evolution even within hundreds of human lifetimes. Although the equations of motion of stars in a star cluster are simple New- tonian, it is impossible to predict precisely history of any star within them to any point in the future. Therefore, we may either compare the observations of different star clusters at different age, we may invent theoretical approaches and analytical predictions, or we must follow their evolution numerically (e.g. with direct N-body integrators) which is the main focus of my research and this thesis. First, we follow the evolution of star clusters in general while coming up with a novel method to estimate their characteristic timescale (i.e. the time of core collapse) based on global parameters. The core collapse is directly linked to the formation of hard binary stars, thus, we focus on their analysis as well. We also follow several recent observational results: (i) ALMA observations of the Serpens South star-forming region indicate that star clusters are born mass...
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Perturbed stellar motion in dense star clusters
Pavlík, Václav ; Šubr, Ladislav (advisor) ; Davies, B. Melvyn (referee) ; Portegies Zwart, Simon (referee)
Star clusters are thought to be the birthplaces of stars as well as the building blocks of galaxies. They typically consist of thousands to millions of stars bound together by self-gravity. These systems evolve on the scale of Myr to Gyr, there- fore, it is impossible for us to see any change in their global evolution even within hundreds of human lifetimes. Although the equations of motion of stars in a star cluster are simple New- tonian, it is impossible to predict precisely history of any star within them to any point in the future. Therefore, we may either compare the observations of different star clusters at different age, we may invent theoretical approaches and analytical predictions, or we must follow their evolution numerically (e.g. with direct N-body integrators) which is the main focus of my research and this thesis. First, we follow the evolution of star clusters in general while coming up with a novel method to estimate their characteristic timescale (i.e. the time of core collapse) based on global parameters. The core collapse is directly linked to the formation of hard binary stars, thus, we focus on their analysis as well. We also follow several recent observational results: (i) ALMA observations of the Serpens South star-forming region indicate that star clusters are born mass...
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The influence of the stellar mass-loss on the dynamics of star clusters
Dinnbier, František ; Jungwiert, Bruno (advisor) ; Šubr, Ladislav (referee)
This work aims at studying the influence of the stellar mass-loss, resulting from the stellar evolution, on the dynamics of massive star clusters. The emphasis has been put on the mass-loss by low-mass and intermediate-mass stars (m < 8 Mo) that form, at the end of their life, a planetary nebula. The expansion speed of gas released by these stars is lower than the escape speed from sufficiently massive star clusters, and the gas can be retained by the cluster. For modelling of the gas hydrodynamics, a simple sticky-particles method was used. To carry out simulations in which gaseous and stellar particles mutually interact through their gravity, substantial modifications had to be realized in the N-body codes Nbody6 and Hermit. For the sake of comparing the influence of stellar mass-loss and relaxation processes, which are happening in the simplified model, two types of simulations were performed: one with the formation of gaseous particles and the other consisting of purely stellar component. The simulations in which the gas component was present showed out a significantly different evolution in the central part of the cluster than those in which the presence of gas was not considered.
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