Spatial evolution of the Helmi streams at four different snapshots in our simulations. The top two rows show the evolution of a progenitor with a stellar mass of 10⁸ M_⊙, while the bottom two rows correspond to a system with a stellar mass of 5 × 10⁶ M_⊙. In both cases, the orbit of the progenitor is the same. The appearance of the debris is seen to depend on the time since accretion as well as on the mass of the progenitor.