On the Stability of Tidal Streams

We explore the stability of tidal streams to perturbations, motivated by recent claims that the clumpy structure of the stellar streams surrounding the globular cluster Palomar 5 are the result of gravitational instability. We calculate the Jeans length of tidal streams by treating them as a thin expanding cylinder of collisionless matter. We also find a general relation between the density and the velocity dispersion inside a stream, which is used to determine the longitudinal Jeans criterion. Our analytic results are checked by following the time evolution of the phase space density within streams using numerical simulations. We conclude that tidal streams within our Galactic halo are stable on all length scales and over all time-scales. DOI: https://doi.org/10.1111/j.1365-2966.2011.18811.x Posted at the Zurich Open Repository and Archive, University of Zurich ZORA URL: https://doi.org/10.5167/uzh-54353 Accepted Version Originally published at: Schneider, A; Moore, B (2011). On the stability of tidal streams. Monthly Notices of the Royal Astronomical Society, 415(2):1569-1576. DOI: https://doi.org/10.1111/j.1365-2966.2011.18811.x Mon. Not. R. Astron. Soc. 000, 1–9 (2011) Printed 27 June 2011 (MN LTEX style file v2.2) On the Stability of Tidal Streams Aurel Schneider and Ben Moore Institute for Theoretical Physics, University of Zurich, Zurich, Switzerland; [email protected]; [email protected]