Dynamics and Mass
From the measurements of the velocities of the various components of M31, it is possible to infer its dynamics and to calculate the mass of material that can explain its kinematics. This field is a complicated one; although in principle there should be no difficulty in deriving the mass distribution and total mass from the rotation curve, in practice there are many details that make a simple solution impossible. For example, there is the composite rotation curve in the inner parts, there is the asymmetry of the motions found at various radial regimes, and there is the problem of the apparent lack of any Keplerian decrease in the velocities in the outermost parts of the galaxy. All of these mean that we do not yet have a complete, detailed model for the dynamics or the mass distribution of M31. We do have an increasingly realistic picture of the complex kinematics and of their implications for our understanding of a galaxy’s structure and motions.
KeywordsBlack Hole Dark Matter Velocity Dispersion Globular Cluster Rotation Curve
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