Abstract The properties of unstable large-scale hydrodynamic (HD) modes of oscillations in the gaseous disk of a flat galaxy with a rotation curve having a velocity jump in the inner region of the disk are numerically investigated. It is shown that some of these modes can form a regular pseudo-ring, and others can generate a spiral structure in a model galactic disk, with the rotation curve that can approximate the observed rotation curves in nearby massive spiral galaxies (such as M31, M81). The characteristic time of formation of the regular structure turns out to be . (1 − 2) GY, the corotation is located in the region of the velocity jump (on the radius∼ 2 − 4 kpc). The properties of the generated densitywaves are determined by the parameters of the velocity jumpon the rotation curve (relative amplitude and steepness of the velocity profile decrease), as well as the temperature (velocity dispersion) of the gas in the disk. For the first time, it was investigated how the global HD modes and the spiral structures formed by them will change in the case of the presence of a jump in the profile of the equilibrium surface density. This model profile was set in the form of a slightly smeared falling density step. Main results were obtained for two-arm m = 2 azimuthal harmonic.

中文翻译：

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旋转曲线上有扭结的扁平星系气态盘中振荡的大尺度流体动力学模式

摘要 数值研究了旋转曲线在盘内区域具有速度跳跃的扁平星系气态盘中不稳定的大尺度流体动力学（HD）振荡模式的性质。结果表明，这些模式中的一些可以形成规则的伪环，而另一些可以在模型星系盘中产生螺旋结构，其旋转曲线可以近似于附近大质量螺旋星系（如M31， M81）。规律结构形成的特征时间为 。(1 − 2) GY，同向旋转位于速度跳跃区域（半径～ 2 − 4 kpc）。生成的密度波的特性由旋转曲线上的速度跳跃参数（速度分布的相对幅度和陡度减小）以及圆盘中气体的温度（速度弥散）决定。首次研究了在平衡表面密度分布中存在跳跃的情况下，全局HD模式及其形成的螺旋结构将如何变化。该模型轮廓以略微涂抹的下降密度步骤的形式设置。主要结果是针对两臂 m = 2 方位角谐波获得的。研究了在平衡表面密度分布中存在跳跃的情况下，全局 HD 模式和由它们形成的螺旋结构将如何变化。该模型轮廓以略微涂抹的下降密度步骤的形式设置。主要结果是针对两臂 m = 2 方位角谐波获得的。研究了在平衡表面密度分布中存在跳跃的情况下，全局 HD 模式和由它们形成的螺旋结构将如何变化。该模型轮廓以略微涂抹的下降密度步骤的形式设置。主要结果是针对两臂 m = 2 方位角谐波获得的。