Journal
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Volume 509, Issue 2, Pages 2443-2456Publisher
OXFORD UNIV PRESS
DOI: 10.1093/mnras/stab3020
Keywords
diffusion; gravitation; galaxies: kinematics and dynamics
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Funding
- French Agence Nationale de la Recherche [ANR-19-CE31-0017]
- Idex Sorbonne Universite
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The study focuses on the amplification of perturbations and the response matrix in stellar clusters, presenting a generic method for calculating damped modes in spherically symmetric stellar clusters. Through testing predictions with direct N-body simulations, a low-frequency weakly damped mode was discovered.
Because all stars contribute to its gravitational potential, stellar clusters amplify perturbations collectively. In the limit of small fluctuations, this is described through linear response theory, via the so-called response matrix. While the evaluation of this matrix is somewhat straightforward for unstable modes (i.e. with a positive growth rate), it requires a careful analytic continuation for damped modes (i.e. with a negative growth rate). We present a generic method to perform such a calculation in spherically symmetric stellar clusters. When applied to an isotropic isochrone cluster, we recover the presence of a low-frequency weakly damped l = 1 mode. We finally use a set of direct N-body simulations to test explicitly this prediction through the statistics of the correlated random walk undergone by a cluster's density centre.
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