  We study numerically a model of non-aligning self-propelled particles
interacting through steric repulsion, which was recently shown to exhibit
active phase separation in two dimensions in the absence of any attractive
interaction or breaking of the orientational symmetry. We construct a phase
diagram in terms of activity and packing fraction and identify three distinct
regimes: a homogeneous liquid with anomalous cluster size distribution, a
phase-separated state both at high and at low density, and a frozen phase. We
provide a physical interpretation of the various regimes and develop scaling
arguments for the boundaries separating them.
