Dynamics of the Disks of Nearby Galaxies

Abstract

I describe how the dynamics of galactic disks can be inferred by imaging and spectroscopy. Next I demonstrate that the decomposition of the rotation curves of spiral galaxies into the contributions by the various components of the galaxies is highly degenerate. Constraints on the decomposition can be found by considering implications for the dynamics of the galactic disks. An important diagnostic is the Toomre Q stability parameter which controls the stability of a galactic disk against local Jeans collapse. I also show how the density wave theory of galactic spiral arms can be employed to constrain the mass of a galactic disk. Applying both diagnostics to the example of NGC 2985 and discussing also the implied mass-to-light ratio I demonstrate that the inner parts of the galaxy, where the optical disk resides, are dominated by baryons. When I apply this method to the disks of low surface brightness galaxies, I find unexpectedly high mass-to light ratios. These could be explained by population synthesis models which assume a bottom heavy initial mass function similar to the recently proposed `integrated galactic initial mass function'.

arXiv comment6 pages, 12 figures, invited contribution to `Galactic and Stellar Dynamics in the era of high resolution surveys', Strasbourg, March 16 -20, 2008

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• The Inner Structure of LambdaCDM Halos III: Universality and Asymptotic Slopes
• The Variation of Integrated Star IMFs among Galaxies
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Cited by in corpus (7)

• Dark matters on the scale of galaxies
• Predictions and Outcomes for the Dynamics of Rotating Galaxies
• Equilibrium Initialization and Stability of Three-Dimensional Gas Disks
• Suppression of gravitational instabilities by dominant dark matter halo in low surface brightness galaxies
• On the nature of IC 3328, an early-type dwarf galaxy with weak spiral structure
• Galaxy Zoo: constraining the origin of spiral arms
• Low-mass disc galaxies and the issue of stability: MOND vs dark matter