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Dark Matter in Spiral Galaxies

Kranz, Thilo

German Title: Dunkle Materie in Spiralgalaxien

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Abstract

This thesis presents a detailed dynamic analysis of five high surface brightness, late type spiral galaxies NGC 3810, NGC 3893, NGC 4254, NGC 5676 and NGC 6643, which were studied with the aim to quantify the luminous-to-dark matter ratio inside their optical radii. In order to meet this goal, the galaxies' morphology and gas kinematics have been observed and compared to hydrodynamic gas simulations which were performed to predict the gas dynamics arising in response to realistic two dimensional gravitational potentials, combined from stellar disk and dark halo contributions. The gravitational potential of the stellar disk was derived from color-corrected NIR photometry and for the dark halo, the mass density distribution of an axisymmetric isothermal sphere with a core was chosen. The rather good agreement between the simulated and observed gas kinematics permitted to conclude that the most massive galaxies tend to possess also very massive stellar disks, dominating the gas dynamics within the optical radius. In less massive galaxies with a maximal rotation velocity of <200 km/s, the mass of the dark halo already equals the stellar mass. The maximal disk stellar mass-to-light ratio in the K-band was found to lie at about M/L_K ~ 0.6. Furthermore, the gas dynamic simulations provide a powerful tool to accurately determine the spiral pattern speed for galaxies, independent of a specific density wave theory. It was found that the location of the corotation resonance falls into a narrow range of around three exponential disk scale lengths for all galaxies from the sample. The corotation resonance encloses the strong part of the stellar spiral in all cases. Based on the experience gained from this project, the use of a color-correction to account for local stellar population differences is strongly encouraged when properties of galactic disks are studied which rely on their stellar mass distributions.

Item Type: Dissertation
Supervisor: Rix, Prof. Hans-Walter
Date of thesis defense: 15. May 2002
Date Deposited: 24. Jun 2002 00:00
Date: 2002
Faculties / Institutes: Service facilities > Max-Planck-Institute allgemein > MPI for Astronomy
Subjects: 530 Physics
Controlled Keywords: Spiralnebel, Galaktischer Halo, Dunkle Materie, Hydrodynamik, Astronomische Beobachtung
Uncontrolled Keywords: Spiral Galaxies , Galactic Dynamics , Dark Matter , Hydrodynamic Computer Simulations , Astronomical Observations
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