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Spiral‐vortex structures generation in gaseous galactic disks with a two‐hump rotation curve
Author(s) -
Torgashin Yu.M.,
Omurkanov T.Z.
Publication year - 2013
Publication title -
astronomische nachrichten
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.394
H-Index - 63
eISSN - 1521-3994
pISSN - 0004-6337
DOI - 10.1002/asna.201311944
Subject(s) - physics , galaxy rotation curve , vortex , spiral (railway) , rotation (mathematics) , density wave theory , spiral galaxy , galaxy , astrophysics , harmonics , angular velocity , centrifugal force , mechanics , rotational speed , classical mechanics , geometry , galaxy formation and evolution , mathematical analysis , quantum mechanics , voltage , mathematics
The hydrodynamic (HD) global modes of oscillations in thin gaseous disks of solitary flat galaxies are numerically investigated. The unstable HD modes are shown to be generated in the gaseous disk when the rotation curve has a velocity “kink” (velocity jump) in the inner disk region (as observed in many nearby spiral galaxies). These unstable HD modes show up as spiral‐vortex dynamical structures with special features, such as growth rates, shape of surface density perturbations, angular pattern speed, etc. Depending on the rotation curve parameters and on the gaseous disk temperature, the properties of unstable modes for the main azimuthal harmonics m = 1–4 are investigated. Along with the centrifugal branch of perturbations, unstable over‐reflection modes are investigated as well, showing a resonance dependence of the growth rate on the temperature of the gaseous disk. The main features of the banana‐like anticyclonic vortices, which form in the perturbed velocity field simultaneously with the spiral density wave, are also studied. The case of the model gaseous disk that approximates the observed one in the M 31 galaxy is studied as application. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)