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Propagating star formation
Dinnbier, František ; Wünsch, Richard (advisor) ; Brož, Miroslav (referee) ; Naab, Thorsten (referee)
Massive stars are powerful energetic sources shaping their surrounding interstellar medium, which is often swept up into a cold dense shell. If the shell fragments and forms a new generation of massive stars, the stars may form new shells, and this sequence repeats recursively leading to propagating star formation. Using three dimensional hydrodynamic simulations, we investigate fragmentation of the shell in order to estimate masses of stars formed in the shell. We develop a new numerical method to calculate the gravitational potential, which enables us to approximate a part of the shell with a plane-parallel layer. Our main results are as follows. Firstly, we compare our numerical calculations to several analytical theories for shell fragmentation, constrain the parameter space of their validity, and discuss the origin of their limitations. Secondly, we report a new qualita- tively different mode of fragmentation - the coalescence driven collapse. While layers with low pressure confinement form monolithically collapsing fragments, layers with high pressure confinement firstly break into stable fragments, which subsequently coalesce. And thirdly, we study whether layers tend to self-organise and form regular patterns as was suggested in literature, and we find no evidence for this conjecture. Based on our...
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Stellar mass-loss in the dynamics of galaxies
Křížek, Miroslav
Title: Stellar mass-loss in galactic dynamics Author: Miroslav Křížek Department: Astronomical Institute of the Charles University Supervisor: RNDr. Bruno Jungwiert, Ph.D., Astronomical Institute - Academy of Sciences of the Czech Republic, v.v.i. and University of California - Riverside Supervisor's e-mail address: bruno@ig.cas.cz Abstract: We present an implementation of the statistical approach to the stars-gas mass exchange cycle into the N-body code. First, we summarize available data on stellar mass-loss and derive the time-dependency of the mass-loss rate of a single stellar population. Since the adopted probabilistic scheme that served as a basis for our implementation was limited to the linear star formation law while observations seem to suggest a non-linearity, we derive the non-linear star formation scheme. Both sides of the mass exchange cycle are then implemented into the code with stellar and gaseous particles and compared with an analytic recipe to test their reliability. In the next step, the comparison of such an extended statistical approach with deterministic scheme is performed for a fully dynamical model. The aim of such comparison is to explore divergence between both models of different natures. As illustration of the code application and sensitivity of the resulting galaxy disk...
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Stellar mass-loss in the dynamics of galaxies
Křížek, Miroslav
Title: Stellar mass-loss in galactic dynamics Author: Miroslav Křížek Department: Astronomical Institute of the Charles University Supervisor: RNDr. Bruno Jungwiert, Ph.D., Astronomical Institute - Academy of Sciences of the Czech Republic, v.v.i. and University of California - Riverside Supervisor's e-mail address: bruno@ig.cas.cz Abstract: We present an implementation of the statistical approach to the stars-gas mass exchange cycle into the N-body code. First, we summarize available data on stellar mass-loss and derive the time-dependency of the mass-loss rate of a single stellar population. Since the adopted probabilistic scheme that served as a basis for our implementation was limited to the linear star formation law while observations seem to suggest a non-linearity, we derive the non-linear star formation scheme. Both sides of the mass exchange cycle are then implemented into the code with stellar and gaseous particles and compared with an analytic recipe to test their reliability. In the next step, the comparison of such an extended statistical approach with deterministic scheme is performed for a fully dynamical model. The aim of such comparison is to explore divergence between both models of different natures. As illustration of the code application and sensitivity of the resulting galaxy disk...
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Propagating star formation
Dinnbier, František ; Wünsch, Richard (advisor) ; Brož, Miroslav (referee) ; Naab, Thorsten (referee)
Massive stars are powerful energetic sources shaping their surrounding interstellar medium, which is often swept up into a cold dense shell. If the shell fragments and forms a new generation of massive stars, the stars may form new shells, and this sequence repeats recursively leading to propagating star formation. Using three dimensional hydrodynamic simulations, we investigate fragmentation of the shell in order to estimate masses of stars formed in the shell. We develop a new numerical method to calculate the gravitational potential, which enables us to approximate a part of the shell with a plane-parallel layer. Our main results are as follows. Firstly, we compare our numerical calculations to several analytical theories for shell fragmentation, constrain the parameter space of their validity, and discuss the origin of their limitations. Secondly, we report a new qualita- tively different mode of fragmentation - the coalescence driven collapse. While layers with low pressure confinement form monolithically collapsing fragments, layers with high pressure confinement firstly break into stable fragments, which subsequently coalesce. And thirdly, we study whether layers tend to self-organise and form regular patterns as was suggested in literature, and we find no evidence for this conjecture. Based on our...
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