Gaps in stellar streams as a result of globular cluster flybys

Context . Thin stellar streams, such as those resulting from the tidal disruption of globular clusters, have long been known and used as probes of the gravitational potential of our Galaxy, both its visible and dark contents. The literature commonly interprets the presence of underdensity regions, or gaps, along these streams as being due to the close passage of dark matter subhalos. Aims . In this work, we investigate the perturbations induced on streams by the passage of dense stellar systems, such as globular clusters themselves, to test the possibility that they may cause the formation of gaps as well. In particular, we focus on the study of the stream generated by a cluster with characteristics (mass, size, and orbit) similar to those of Palomar 5, a well-known globular cluster in the Galactic halo that has particularly long tidal tails. Methods . For this purpose, we used a particle-test code to simulate the formation and evolution of the stream when subjected to the Galaxy’s gravitational field plus its whole system of globular clusters. Results . Our study shows that such a stream can be strongly perturbed by the close passage of other clusters, in particular NGC 2808, NGC 7078, and NGC 104, and that these perturbations induce the formation of gaps in the tails. Conclusions . The results of this work show that globular clusters can induce gaps in cold streams–just as it has been demonstrated in the literature for that other baryonic components, such as giant molecular clouds and the Galactic bar. Therefore, a future work that attempts to infer the dark matter subhalo distribution from stellar stream gaps must include the contributions from globular clusters.