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	Stationary perturbation configurations in a composite system of stellar and coplanarly magnetized gaseous singular isothermal discs
	Yu-Qing Lou ; Yue Zou
	2010-05-06 ; 2010-05-06
关键词	Bibliography Theoretical or Mathematical/ clusters of galaxies dark matter galaxies intergalactic magnetic fields perturbation theory/ stationary perturbation configurations composite system stellar discs gaseous singular isothermal discs gravity disc galaxy axisymmetric background equilibrium surface mass density rotation curves radial scaling parameter space dimensionless parameters Alfven speed stellar velocity dispersion gas sound speed azimuthal periodicity bar-like instability axisymmetric equilibrium total kinetic energy gravitational potential energy total magnetic energy gravitational effect dark matter halo azimuthal magnetic field perturbation global perturbation solutions magnetohydrodynamic codes/ A9850K Groups, clusters, and superclusters of galaxies A9850T Intergalactic and intracluster matter A9850E Galactic structure, content and morphology A9850D Kinematics, dynamics, and rotation of galaxies
中文摘要	We construct aligned and unaligned stationary perturbation configurations in a composite system of stellar and coplanarly magnetized gaseous singular isothermal discs (SIDs) coupled by gravity. This study extends zrecent analyses on (magnetized) SIDs by Shu et al. (2000), Lou (2002) and Lou & Shen (2003). By this model, we intend to provide a conceptual framework to gain insights for multiwavelength large-scale structural observations of disc galaxies. Both SIDs are approximated to be razor thin and are in a self-consistent axisymmetric background equilibrium with power-law surface mass densities and flat rotation curves. The gaseous SID is embedded with a coplanar azimuthal magnetic field B/sub thetas /(r) of a radial scaling r/sup - 1/2 / that is not force-free. In comparison with the SID problems studied earlier, there are three possible classes of stationary solutions allowed by more dynamic freedoms. To identify physical solutions, we explore parameter space involving three dimensionless parameters: ratio lambda of Alfven speed to sound speed in the magnetized gaseous SID; ratio beta of the square of the stellar velocity dispersion to the gas sound speed; and ratio delta of the surface mass densities of the two SIDs. For both aligned and unaligned spiral cases with azimuthal periodicities |m| >or= 2, one of the three solution branches is always physical, while the other two branches might become invalid when beta exceeds certain critical values. For the onset criteria from an axisymmetric equilibrium to aligned secular bar-like instabilities, the corresponding T /| W - M | ratio, which varies with lambda , beta and delta , may be considerably lower than the oft-quoted value of T /| W | ~ 0.4, where T is the total kinetic energy, W is the total gravitational potential energy and M is the total magnetic energy. For unaligned spiral cases, we examine marginal instabilities for axisymmetric (|m| = 0) and nonaxisymmetric (|m| > 0) disturbances. The resulting marginal stability curves differ from the previous ones. The case of a composite partial magnetized SID system is also investigated to include the gravitational effect of an axisymmetric dark matter halo on the SID equilibrium. We further examine the phase relationship among the mass densities of the two SIDs and azimuthal magnetic field perturbation. Our exact global perturbation solutions and critical points are valuable for testing numerical magnetohydrodynamic codes. For galactic applications, our model analysis contains more realistic elements and offers useful insights into the structures and dynamics of disc galaxies consisting of stars and magnetized gas.
语种	英语 ; 英语
出版者	Blackwell Science for R. Astron. Soc ; UK
内容类型	期刊论文
源URL	[http://hdl.handle.net/123456789/14628]
专题	清华大学
推荐引用方式 GB/T 7714	Yu-Qing Lou,Yue Zou. Stationary perturbation configurations in a composite system of stellar and coplanarly magnetized gaseous singular isothermal discs[J],2010, 2010.
APA	Yu-Qing Lou,&Yue Zou.(2010).Stationary perturbation configurations in a composite system of stellar and coplanarly magnetized gaseous singular isothermal discs..
MLA	Yu-Qing Lou,et al."Stationary perturbation configurations in a composite system of stellar and coplanarly magnetized gaseous singular isothermal discs".(2010).

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