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arXiv · 0811.2946

Peculiarities in the stellar velocity distribution of galaxies with a two-armed spiral structure

E. I. Vorobyov·Christian Theis
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Abstract

We expand our pervious numerical study of the properties of the stellar velocity distribution within the disk of a two-armed spiral galaxy by considering spiral stellar density waves with different global Fourier amplitudes, C_2. We confirm our previous conclusion that the ratio σ_1:σ_2 of smallest versus largest principal axes of the stellar velocity ellipsoid becomes abnormally small near the outer edges of the stellar spiral arms. The extent to which the stellar velocity ellipsoid is elongated (as compared to the unperturbed value typical for the axisymmetric disk) increases with the strength of the spiral density wave. In particular, the C_2=0.06 spiral can decrease the unperturbed value of σ_1:σ_2 by 20%, while the C_2=0.13 spiral can decrease the unperturbed σ_1:σ_2 by a factor of 3. The abnormally small values of the σ_1:σ_2 ratio can potentially be used to track the position of {\it stellar} spiral density waves. The σ_{ϕϕ}:σ_{rr} ratio is characterized by a more complex behaviour and exhibits less definite minima near the outer edges of the spiral arms. We find that the epicycle approximation is violated near the spiral arms and cannot be used in spiral galaxies with C_2 >= 0.05-0.06 or in galaxies with the amplitude of the spiral stellar density wave (relative to the unperturbed background) of order 0.1 or greater.

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E. I. Vorobyov, Christian Theis. 2008-11-18. Peculiarities in the stellar velocity distribution of galaxies with a two-armed spiral structure. https://doi.org/10.1002/asna.200811092

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