Type Ibc SNe in disturbed galaxies

When the galaxies are split into "disturbed" and "undisturbed" categories, a striking difference emerges. The disturbed galaxies have a central excess of CCSNe and this excess is almost completely dominated by supernovae of types Ib, Ic, and Ib/c, whereas type II supernovae dominate in all other environments.

The difference cannot easily be explained by metallicity or extinction effects, and thus we propose that this is direct evidence for a stellar initial mass function that is strongly weighted toward high-mass stars, specifically in the central regions of disturbed galaxies.