Abstract:
It is argued that all SNI come from short-lived stars and do not occur in a typical, isolationist, gas-free early-type galaxy. SNI occur only in those galaxies which accrete gas and form stars. SN properties of E/SOs are, therefore, determined by environmental factors. Presence of gas and dust in early-type galaxies, SN occurrence, nuclear emission, and radio-activity are all manifestations of the same phenomenon, namely availability of gas.
What is now urgently required is multi-colour photometry of supernovic early-type galaxies around the regions of recorded SN to see if there are signs of recent star-formation.
