Due to an unfortunate error occurred during production, refs. [21] and [22] have been wrongly renumbered in the bibliography on the last page of the paper. The correct numbering is given here below: [21] Stukowski A., Visualization and analysis of atomistic simulation data with OVITO-the Open Visualization Tool, Modelling Simul. Mater. Sci. Eng., 18 (2010) 015012. [22] Kosterlitz J. M., J. Phys. C: Solid State Phys., 7 (1974) 1046. The reference numbering within the main text need no correction. We deeply apologize to the authors for the unwanted mistake.

Many biological systems form colonies at high density. Passive granular systems will be jammed at such densities, yet for the survival of biological systems it is crucial that they are dynamic. We construct a phase diagram for a system of active particles interacting via Vicsek alignment, and vary the density, self-propulsion force, and orientational noise. We find that the system exhibits four different phases, characterized by transitions in the effective diffusion constant and in the orientational order parameter. Our simulations show that there exists an optimal noise such that particles require a minimal force to unjam, allowing for rearrangements.