Universität zu Köln

Ali, Basel (2023). Orbital and Dynamical Investigation of the Galactic Center S-cluster. PhD thesis, Universität zu Köln.

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Abstract

At the center of the Milky Way resides the so-called the S-cluster, orbiting the super massive black hole on highly elliptical orbits. In this research, I use the data obtained from the Very Large Telescope in Chile to analyse the dynamics and structure of this cluster. In the first attempt and using visual inspection of the orbits, I find that a sample of 32 orbits are arranged in two highly inclined perpendicular disks with each disk containing clockwise and anti-clockwise directions. In the second project, which was established to obtain orbital solutions for 71 stars that lack radial velocity measurements, I explore 8 different approaches that belong to Markov chain Monte Carlo, approximate Bayesian computations and nested sampling. The findings show that nested sampling outperforms both MCMC and ABC and hence it is used for further application. Finally, in the last project, I use machine learning clustering algorithms after obtaining a sample of 20 orbits using Ultranest to cluster the specific angular momentum vectors in 3D to find any prominent structure. The analysis show that the majority of 57 orbits are organized in a system of three highly inclined disks, two of which are closely oriented in space, while both being perpendicular to a thicker more populated disk, which might be connected to the already identified clockwise rotating disk further away. In summary, this research reveals that the existence of stellar disks in the vicinity of SMBH is possible and the S-cluster could have originated rather locally. Nevertheless, detailed N-body simulations are required to form a solid conclusion about the formation of this system and its current structural configurations.

Item Type:	Thesis (PhD thesis)
Creators:	Creators Email ORCID ORCID Put Code Ali, Basel Baselali1992@gmail.com UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-714894
Date:	31 October 2023
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Physics > Institute of Physics I
Subjects:	Physics
Uncontrolled Keywords:	Keywords Language Galactic center, stellar dynamics, black holes, Bayesian computations, machine learning clutering UNSPECIFIED
Date of oral exam:	14 July 2023
Referee:	Name Academic Title Eckart, Andreas Prof. Dr. Schilke, Peter Prof. Dr
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/71489