Generation of mock tidal streams

Abstract

In this paper, we discuss a method for the generation of mock tidal streams. Using an ensemble of simulations in an isochrone potential where the actions and frequencies are known, we derive an empirical recipe for the evolving satellite mass and the corresponding mass-loss rate, and the ejection conditions of the stream material. The resulting stream can then be quickly generated either with direct orbital integration, or by using the action-angle formalism. The model naturally produces streaky features within the stream. These are formed due to the radial oscillation of the progenitor and the bursts of stars emitted near per centre, rather than clumping at particular oscillation phases as sometimes suggested. When detectable, these streaky features are a reliable diagnostic for the stream's direction of motion and encode other information on the progenitor and its orbit. We show several tests of the recipe in alternate potentials, including a case with a chaotic progenitor orbit which displays a marked effect on the width of the stream. Although the specific ejection recipe may need adjusting when elements such as the orbit or satellite density profile are changed significantly, our examples suggest that model tidal streams can be quickly and accurately generated by models of this general type for use in Bayesian sampling.