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Journal Articles Monthly Notices of the Royal Astronomical Society Year : 2019

Instabilities in disc galaxies: from noise to grooves to spirals

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1
Sven de Rijcke
  • Function : Author
Jean-Baptiste Fouvry
  • Function : Author

Abstract

Using the linearized Boltzmann equation, we investigate how grooves carved in the phase space of a half-mass Mestel disc can trigger the vigorous growth of two-armed spiral eigenmodes. Such grooves result from the self-induced dynamics of a disc subject to finite-N shot noise, as swing-amplified noise patterns push stars towards lower angular momentum orbits at their inner Lindblad radius. Supplementing the linear theory with analytical arguments, we show that the dominant spiral mode is a cavity mode with reflections off the forbidden region around corotation and off the deepest groove. Other subdominant modes are identified as groove modes. We provide evidence that the depletion of near-circular orbits, and not the addition of radial orbits, is the crucial physical ingredient that causes these new eigenmodes. Thus, it is possible for an isolated, linearly stable stellar disc to spontaneously become linearly unstable via the self-induced formation of phase-space grooves through finite-N dynamics. These results may help explain the growth and maintenance of spiral patterns in real disc galaxies.
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Dates and versions

insu-03747937 , version 1 (09-08-2022)

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Sven de Rijcke, Jean-Baptiste Fouvry, Christophe Pichon. Instabilities in disc galaxies: from noise to grooves to spirals. Monthly Notices of the Royal Astronomical Society, 2019, 484, pp.3198-3208. ⟨10.1093/mnras/stz166⟩. ⟨insu-03747937⟩
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