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Analysing stellar motions and spiral arm formation in spiral galaxies

Author: Robert Grand

Mullard Space Science Laboratory (UCL)

Co-Authors: Daisuke Kawata, Mark Cropper

Session: GAL: Physics of galaxies at high and low redshift (includes Milky Way)

Presentation type: Poster

Summary:

Spiral density wave theory (SDWT) states that the spiral pattern is a long lived wave structure, in that a spiral arm is analogous to the crest of a wave in the ocean; not necessarily consisting of the same stars as it evolves, but maintaining the high density of a wave peak. It also states that the spiral arms rotate at fixed (pattern) speeds, constant over radius and time. We run several N-body simulations of Milky Way size disk galaxies, and study how spiral arms develop and affect the motions of stellar particles throughout their lives. We find that the spiral arms are recurrent material features, and the pattern speed generally decreases with radius, in such a way that the pattern speed almost equals the rotation speed of stars at all radii. We demonstrate that such spiral arms induce strong radial migration of the stellar component and discuss how the orbits of stars are related to the recurrent nature of the spiral arms.