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The internal kinematics of globular clusters. An intimate view, from models to observations

Bianchini, Paolo

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Globular clusters (GCs) were long believed to be simple, non-rotating, isotropic and spherical stellar systems with all of their stars formed approximately 13 Gyr ago. However, their origin in the early epochs of galaxy formation is still debated. Growing evidence is now showing a larger degree of complexity in their structure, morphology, stellar populations and internal dynamics. The goal of this Thesis is to unveil the com- plexity of their current dynamical properties and to connect it to their formation and subsequent dynamical evolution. As a first step, I show that the study of the morphology alone is not enough in order to disentangle the formation of GCs, in particular to distinguish clusters that formed in-situ from clusters that were accreted. This motivated the detailed exploration of their internal kinematics, that provides a long lasting “fossil record” of the dynamical processes that a GC has experience during its long-term evolution. Using a combination of state-of-the-art kinematic observations and dynamical modeling, I carry out the study of the kinematic effects connected to the presence of intermediate-mass black holes, binary stars and the onset of energy equipartition. In particular, I focus on the understanding of the systematics and biases present in the integrated-light kinematic observations and Hubble Space Telescope proper motion samples, making use of mock observations constructed directly from the dynamical models. This strategy gives the direct advantage of achieving a sound interpretation of the observations and of the physical processes described by the models. Having reached a deeper understanding of the data, I set up a first step to trace the evolution of GCs, based on their current kinematics. I show that the degree of energy equipartition attained by a GC can be connected to its dynamical state and therefore used as an indicator of its formation or peculiar dynamical evolution. My work indicates that the synergy between models, observations and the study of the internal kinematics of GCs is the key to unveil their dynamical state. This will be the starting point for exploiting at full power the comprehensive amount of data that will be delivered by the Gaia mission and in the approaching era of Extremely Large Telescopes.

Item Type: Dissertation
Supervisor: van de Ven, Dr. Glenn
Date of thesis defense: 19 July 2016
Date Deposited: 24 Aug 2016 12:04
Date: 2016
Faculties / Institutes: The Faculty of Physics and Astronomy > Dekanat der Fakultät für Physik und Astronomie
Subjects: 520 Astronomy and allied sciences
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