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Self-Gravity, Resonances & Orbital diffusion in stellar discs

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Fluctuations in a stellar system’s gravitational field cause the orbits of stars to evolve. The resulting evolution of the system can be computed with the orbit-averaged dressed Fokker-Planck equation in angle-actions coordinates. I will present the formalism that enables one to compute the diffusion tensor from a given source of noise in the gravitational field when the system’s dynamical response to that noise is included. In the case of a cool stellar disc we are able to reduce the computation of the diffusion tensor to a one-dimensional integral. The shot-noise-driven formation of narrow ridges of resonant orbits is therefore recovered in the WKB limit of tightly wound transient spirals, for a tepid Toomre-stable tapered disc, so that we are able to explain analytically the principal features of numerical simulations of such discs.

This talk is part of the Institute of Astronomy Galaxies Discussion Group series.

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