Abstract
AbstractWe expand our previous numerical study of the properties of the stellar velocity distribution within the disk of a twoarmed spiral galaxy by considering spiral stellar density waves with different global Fourier amplitudes, C2. We confirm our previous conclusion that the ratio σ1: σ2 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 C2 = 0.06 spiral can decrease the unperturbed value of σ1: σ2 by 20%, while the C2 = 0.13 spiral can decrease the unperturbed σ1: σ2 by a factor of 3. The abnormally small values of the σ1: σ2 ratio can potentially be used to track the position of stellar spiral density waves. The σϕϕ: σrr 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 C2 ≳ 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. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
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