Paper detail

On the multiple supernova population of Arp 299: constraints on progenitor properties and host galaxy star formation characteristics

Throughout the last 20 years 7 supernovae (SNe) have been discovered within Arp 299. One of these is unclassified, leaving 6 core-collapse events; 2 type II, 2 type Ib, a type IIb and one object of indistinct type; Ib/IIb. We analyse the relative numbers of these types, together with their positions with respect to host galaxy properties, to investigate implications for both progenitor characteristics and star formation (SF) properties. Our findings are: 1) the ratio of 'stripped envelope' (SE) events to other type II is higher than that found in the local Universe. 2) All SE SNe are more centrally concentrated within the system than the other type II. 3) All SN environments have similar metallicities and there are no significant metallicity gradients across the system. 4) The SE SNe all fall on bright SF regions while the other type II are found to occur away from bright HII regions. We draw two different -but non-mutually exclusive- interpretations on the system and its supernovae: 1) The distribution of SNe, and the relatively high fraction of types Ib and IIb events over other type II can be explained by the young age of the most recent SF in the system, where insufficient time has expired for the observed to match the 'true' relative SN rates. This explanation provides additional independent evidence that both types Ib and IIb SNe arise from progenitors of shorter stellar lifetime and hence higher mass than other type II. 2) Given the assumption that types Ib and IIb trace higher mass progenitor stars, the relatively high frequency of types Ib and IIb to other type II, and also the centralisation of the former over the latter with respect to host galaxy light implies that in the centrally peaked and enhanced SF within this system, the initial mass function is biased towards the production of high mass stars.