Linear response of galactic haloes to adiabatic gravitational perturbations |
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| Authors: | Chigurupati Murali & Scott Tremaine |
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| Institution: | Canadian Institute for Theoretical Astrophysics, McLennan Labs, University of Toronto, 60 St. George Street, Toronto M5S 3H8, Canada,;Canadian Institute for Advanced Research, Program in Cosmology and Gravity |
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| Abstract: | We determine the response of a self-similar isothermal stellar system to small adiabatic gravitational perturbations. For odd spherical harmonics the response is identical to the response of the analogous isothermal fluid system. For even spherical harmonics the response can be regarded as an infinite series of wavetrains in log r , implying alternating compression and rarefaction in equal logarithmic radius intervals. Partly because of the oscillatory nature of the solutions, tidal fields from external sources are not strongly amplified by an intervening isothermal stellar system, except at radii ?10?3.5 times the satellite radius; at some radii the stellar system can even screen the external tidal field in a manner analogous to Debye screening. As Weinberg has pointed out, individual resonances in a stellar system can strongly amplify external tidal fields over a limited radial range, but we cannot address this possibility because we examine only adiabatic perturbations. We also discuss the application of our method to the halo response caused by the slow growth of an embedded thin disc. |
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| Keywords: | celestial mechanics stellar dynamics galaxies: haloes galaxies: individual: Milky Way galaxies: kinematics and dynamics |
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