Understanding the Formation and Evolution of Nuclei in Galaxies using N-body Simulations

Hartmann, Markus (2011) Understanding the Formation and Evolution of Nuclei in Galaxies using N-body Simulations. Doctoral thesis, University of Central Lancashire.

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Central massive objects like supermassive black holes and stellar nuclear clusters are common in all type of galaxies. I use N-body simulations to study the formation and evolution of nuclear clusters and to investigate the influence of the dynamical evolution of disc galaxies on the structural and kinematical properties of the host galaxy. I show that the second moment of velocities determine a lower limit on the dissipative formation process, which is about 50% in the case of the nuclear cluster in the late-type spiral galaxy NGC 4244. The vertical anisotropy of nuclear clusters can be used to determine an upper limit on the formation process due to merger or accretion of star clusters, which is about 10% for the nuclear cluster in NGC 4244. This is the first time that we have strong evidence of a hybrid formation scenario for nuclear clusters. In a set of 25 galaxy simulations I study bar formation in disc galaxies. I show that bar formation lead to the increase in mass in the central region of galaxies. This mass increase raises the velocity dispersion of stars in the disc and bulge component, which explains the offset of barred galaxies in the relation between the mass of the supermassive black hole, M, and the velocity dispersion of stars in the bulge, e , the M - e relation (Gueltekin et al. 2009). While Graham et al. (2011) argued that the orbital structure of stars within the bar could be responsible for the observed offset of barred galaxies from the M - e relation of unbarred galaxies, I show that the effect of stellar orbits in bars on e is less than 15% compared to the increase in mass which raises e by 40%. The offset I find in the simulation is comparable to the offset using the recent sample of M measurements of elliptical, unbarred and barred disc galaxies from Gueltekin et al. (2009).

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