Abstract

It has long been established that the properties of type Ia supernovae (SNe Ia) depend on their local environment, even after typical standardisation methods. This is typically referred to as the mass step, where SNe Ia in high-mass galaxies are on average brighter than their low-mass counterparts post-standardisation, although trends have been established with other environmental properties including colour, specific star formation rate and distance from the centre of the galaxy. There has been ongoing debate in the field about whether these differences are intrinsic or just the result of extrinsic effects i.e. dust. I will present recent analysis of the environmental dependence of SNe Ia which have found an intrinsic contribution to the mass step, with particularly strong differences around the i-band secondary maximum. These results demonstrate that there are intrinsic differences between SNe Ia in different environments and raise an interesting question about what is driving these results; understanding this finding can help reveal the underlying physical cause of the environmental dependence of SNe Ia.