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Neutron stars near a galactic centre
Zajaček, Michal ; Karas, Vladimír (advisor) ; Šubr, Ladislav (referee)
In this work we study the processes near the Galactic centre, which serves as a paradigm for low- luminosity galactic nuclei. The introductory part of the thesis is a brief review on the radio source Sagittarius A* in the Galactic centre and on its immediate surroundings. The main part of the thesis focuses on the hypothetical population of neutron stars that should be present in large numbers in this region. We analyse the predictions concerning the encounters of this observationally unexplored population with the ambient interstellar medium and we discuss the distribution of their interaction modes with respect to the parameters of the system. We find out that this distribution is strongly dependent on the density of the ambient medium, whereas only weakly dependent on its temperature. The effect of the prolongation of rotational period is negligible on the time-scale of about ten thousand years. In the second part, we predict the evolution of the high-eccentricity passages of clouds and dust- enshrouded stars (with pericentre distances at about 1000 Schwarzschild radii from the black hole). In all studied cases a major part of the matter is diverted from the original path. Powered by TCPDF (www.tcpdf.org)
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Velké pozdní bombardování v různých místech sluneční soustavy
Zajaček, Michal ; Brož, Miroslav (advisor) ; Ďurech, Josef (referee)
In this work, we study the Late Heavy Bombardment (LHB) in the Solar System which took place from 4.1 to 3.8 billion years ago, and represents a period of intense collisions whose traces are observed on the Moon and other bodies mainly in the form of craters or impact melts. The first part of the thesis is a review on the LHB with the focus on observational evidence and recent dynamical models. In the second part, we test a particular dynamical model of the LHB using the observed cratering records on various Solar-System bodies, which was not done previously to such an extent. For this purpose, we use the symplectic integrator SyMBA, the collisional code Boulder, and various projectile-crater scaling laws. We discuss the sources of uncertainties of the observations as well as that of the models. Furthermore, we use our results to constrain the size-frequency distribution of the primordial cometary population.
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Neutron stars near a galactic centre
Zajaček, Michal
In this work we study the processes near the Galactic centre, which serves as a paradigm for low- luminosity galactic nuclei. The introductory part of the thesis is a brief review on the radio source Sagittarius A* in the Galactic centre and on its immediate surroundings. The main part of the thesis focuses on the hypothetical population of neutron stars that should be present in large numbers in this region. We analyse the predictions concerning the encounters of this observationally unexplored population with the ambient interstellar medium and we discuss the distribution of their interaction modes with respect to the parameters of the system. We find out that this distribution is strongly dependent on the density of the ambient medium, whereas only weakly dependent on its temperature. The effect of the prolongation of rotational period is negligible on the time-scale of about ten thousand years. In the second part, we predict the evolution of the high-eccentricity passages of clouds and dust- enshrouded stars (with pericentre distances at about 1000 Schwarzschild radii from the black hole). In all studied cases a major part of the matter is diverted from the original path. Powered by TCPDF (www.tcpdf.org)
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Missing bright red giants in the Galactic center: A fingerprint of its once active state?
Zajaček, Michal ; Araudo, Anabella ; Karas, Vladimír ; Czerny, B. ; Eckart, A. ; Suková, Petra ; Štolc, Marcel ; Witzany, V.
We propose a novel scenario for the bright red-giant depletion based onthe collisions between red giants and the nuclear jet, which was likely active in the Galactic center a few million years ago and could have led to the formation of the large-scaleγ-ray Fermi bubbles. The process of the jet-induced ablation of red giants appears to be most efficient within∼0.04 pc(S-cluster), while at larger distances it was complemented by star–accretion disc collisions and at smaller scales, tidal stripping operated. These three mechanisms likely operated simultaneously and createdan apparent core of late-type stars within∼0.5 pc.
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Neutron stars near a galactic centre
Zajaček, Michal
In this work we study the processes near the Galactic centre, which serves as a paradigm for low- luminosity galactic nuclei. The introductory part of the thesis is a brief review on the radio source Sagittarius A* in the Galactic centre and on its immediate surroundings. The main part of the thesis focuses on the hypothetical population of neutron stars that should be present in large numbers in this region. We analyse the predictions concerning the encounters of this observationally unexplored population with the ambient interstellar medium and we discuss the distribution of their interaction modes with respect to the parameters of the system. We find out that this distribution is strongly dependent on the density of the ambient medium, whereas only weakly dependent on its temperature. The effect of the prolongation of rotational period is negligible on the time-scale of about ten thousand years. In the second part, we predict the evolution of the high-eccentricity passages of clouds and dust- enshrouded stars (with pericentre distances at about 1000 Schwarzschild radii from the black hole). In all studied cases a major part of the matter is diverted from the original path. Powered by TCPDF (www.tcpdf.org)
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Neutron stars near a galactic centre
Zajaček, Michal ; Karas, Vladimír (advisor) ; Šubr, Ladislav (referee)
In this work we study the processes near the Galactic centre, which serves as a paradigm for low- luminosity galactic nuclei. The introductory part of the thesis is a brief review on the radio source Sagittarius A* in the Galactic centre and on its immediate surroundings. The main part of the thesis focuses on the hypothetical population of neutron stars that should be present in large numbers in this region. We analyse the predictions concerning the encounters of this observationally unexplored population with the ambient interstellar medium and we discuss the distribution of their interaction modes with respect to the parameters of the system. We find out that this distribution is strongly dependent on the density of the ambient medium, whereas only weakly dependent on its temperature. The effect of the prolongation of rotational period is negligible on the time-scale of about ten thousand years. In the second part, we predict the evolution of the high-eccentricity passages of clouds and dust- enshrouded stars (with pericentre distances at about 1000 Schwarzschild radii from the black hole). In all studied cases a major part of the matter is diverted from the original path. Powered by TCPDF (www.tcpdf.org)
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Velké pozdní bombardování v různých místech sluneční soustavy
Zajaček, Michal ; Brož, Miroslav (advisor) ; Ďurech, Josef (referee)
In this work, we study the Late Heavy Bombardment (LHB) in the Solar System which took place from 4.1 to 3.8 billion years ago, and represents a period of intense collisions whose traces are observed on the Moon and other bodies mainly in the form of craters or impact melts. The first part of the thesis is a review on the LHB with the focus on observational evidence and recent dynamical models. In the second part, we test a particular dynamical model of the LHB using the observed cratering records on various Solar-System bodies, which was not done previously to such an extent. For this purpose, we use the symplectic integrator SyMBA, the collisional code Boulder, and various projectile-crater scaling laws. We discuss the sources of uncertainties of the observations as well as that of the models. Furthermore, we use our results to constrain the size-frequency distribution of the primordial cometary population.
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