On the environments of Type Ia supernovae within host galaxies

Abstract

We present constraints on Type Ia supernovae (SNe Ia) progenitors through an analysis of the environments found at the explosion sites of 102 events within star-forming host galaxies. Ha and Galaxy Evolution Explorer near-ultraviolet (UV) images are used to trace on-going and recent star formation (SF), while broad-band B, R, J, K imaging is also analysed. Using pixel statistics we find that SNe Ia show the lowest degree of association with Ha emission of all supernova (SN) types. It is also found that they do not trace near-UV emission. As the latter traces SF on time-scales less than 100 Myr, this rules out any extreme 'prompt' delay times as the dominant progenitor channel of SNe Ia. SNe Ia best trace the B-band light distribution of their host galaxies. This implies that the population within star-forming galaxies is dominated by relatively young progenitors. Splitting SNe by their (B - V) colours at maximum light, 'redder' events show a higher degree of association with H II regions and are found more centrally within hosts. We discuss possible explanations of this result in terms of line-of-sight extinction and progenitor effects. No evidence for correlations between SN stretch and environment properties is observed.