Wednesday 20 Nov 2013Spiral Arms in Numerical Simulations of Disc Galaxies

Dr Daisuke Kawata - MSSL, UCL

Physics, 4th floor 14:00-15:00

Recently numerical simulation studies, including Grand, Kawata & Cropper (2012ab, 2013), are claiming that the long-lived spiral arms suggested by the classical density wave theory of Lin & Shu (1964) are difficult to be reproduced by numerical simulations with self-gravity. Using our improved galactic chemodynamics N-body/SPH code, GCD+ (Kawata et al. 2013), we demonstrate that the spiral arms in our simulations are winding, transient and recurrent features whose pattern speeds decrease with radius, similar to the rotation speed of stars. We found that such co-rotating spiral arms induce systematic stellar motion along the arm in the radial direction and stars migrate toward the outer (inner) radii on the trailing (leading) side of the arm at all the radii. We also show that the phase of epicycle motion and the azimuthal position with respect to the spiral arm are the important criteria for the stars that radially migrate. We discuss the observational consequence of such winding spiral arms, including the azimuthal offset of spiral arms traced by different stellar populations (Ferreras et al. 2012) and the correlation between the pitch angle and the shape of the rotation curve (Grand et al. 2013).

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