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	Global axisymmetric stability analysis for a composite system of two gravitationally coupled scale-free discs
	Shen, Y ; Lou, YQ
	2010-05-06 ; 2010-05-06
关键词	hydrodynamics ISM : general galaxies : kinematics and dynamics galaxies : spiral galaxies : structure waves SINGULAR ISOTHERMAL DISCS SPIRAL GALAXIES DENSITY WAVES PERTURBATION CONFIGURATIONS 2-FLUID SYSTEM GALACTIC DISK GAS STELLAR MODES INSTABILITIES Astronomy & Astrophysics
中文摘要	For a composite system of gravitationally coupled stellar and gaseous discs, we have carried out a linear stability analysis for axisymmetric coplanar perturbations using the two-fluid formalism. The background stellar and gaseous discs are taken to be scale-free with all physical variables varying as powers of the cylindrical radius r with compatible exponents. The unstable modes set in as neutral modes or stationary perturbation configurations with angular frequency omega = 0. The axisymmetric stable range is bounded by two marginal stability curves derived from stationary perturbation configurations. Because of the gravitational coupling between the stellar and the gaseous discs, one only needs to consider the parameter regime of the stellar disc. There exist two unstable regimes in general: a collapse regime corresponding to large-scale perturbations and a ring-fragmentation regime corresponding to short-wavelength perturbations. The composite system will collapse if it rotates too slowly and will succumb to ring-fragmentation instabilities if it rotates sufficiently fast. The overall stable range against axisymmetric perturbations is determined by a necessary D-criterion involving the effective Mach number squared D-s(2) (the squared ratio of the stellar disc rotation speed to the stellar velocity dispersion up to a numerical factor). Different mass ratio delta and sound speed ratio, eta of the gaseous and stellar disc components will alter the overall stability. For spiral galaxies or circumnuclear discs, we further include the dynamical effect of a massive dark matter halo. Astrophysical applications to disc galaxies, proto-stellar discs and circumnuclear discs are given as examples.
语种	英语 ; 英语
出版者	SCIENCE CHINA PRESS ; BEIJING ; 16 DONGHUANGCHENGGEN NORTH ST, BEIJING 100717, PEOPLES R CHINA
内容类型	期刊论文
源URL	[http://hdl.handle.net/123456789/15133]
专题	清华大学
推荐引用方式 GB/T 7714	Shen, Y,Lou, YQ. Global axisymmetric stability analysis for a composite system of two gravitationally coupled scale-free discs[J],2010, 2010.
APA	Shen, Y,&Lou, YQ.(2010).Global axisymmetric stability analysis for a composite system of two gravitationally coupled scale-free discs..
MLA	Shen, Y,et al."Global axisymmetric stability analysis for a composite system of two gravitationally coupled scale-free discs".(2010).

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