Fragmentation of ring galaxies and transformation to clumpy galaxies

We study the fragmentation of collisional ring galaxies (CRGs) using a linear perturbation analysis that computes physical conditions gravitational instability, as determined by balance self-gravity against pressure and Coriolis forces. adopt our formalism to simulations CRGs show can accurately characterise stability onset fragmentation, although theory appears under-predict number fragments an unstable CRG factor 2. In addition, since orthodox `density-wave' model is inapplicable such self-gravitating rings, we devise simple approach describes rings propagating material waves. find toy predict whether simulated fragment or not information from their pre-collision states. also apply instability discovered at high redshift, $z=2.19$. quite velocity dispersion required for ring, therefore should be fragmentation. are rarely observed redshifts, this may because usually too faint. Since induce active star formation make bright enough observe, could explain rarity. An into massive clumps retaining initial disc rotation, thus it would evolve clumpy galaxy with low surface density in inter-clump region.