Supernovae (SNe) are the main driver of chemical enrichment of the interstellar medium in galaxies by propelling the elements created in the interior of their progenitor stars and during the explosion. However, the ultimate link between different kinds of SNe and their progenitor systems is far from being solved, and it is currently one of the most important unanswered questions in astrophysics. Several attempts to constrain the nature of the progenitors associated to each SN type have centered efforts in searching for pre-explosion images of nearby galaxies in publicly available archives, but the efficiency of this method is limited by the presence and depth of archival high-resolution observations at the exact SN location, which is very scarce, and by the SN rate in the local Universe, that is lower in the volume where high-resolution data is available.
Single-star evolution models predict that massive stars (greater than 8 solar masses, M⊙) keep burning elements in their interiors by nuclear fusion until forming a heavy iron core tens of millions of years (Myr) after their birth. At this point, the star gravitationally collapses into a neutron star or a black hole ejecting the star’s outer envelope in a big explosion, which we call core-collapse supernova (CC SN). In this picture, the higher limit in the lifetime of a massive star that produces CC SNe is around 40 Myr, corresponding to the lower mass limit of around 8 M⊙. Binary system models instead, predict that intermediate mass stars, as low as 4 M⊙, may end as CC SNe. This lower limit correspond to longer stellar lifetimes, and the sharp age cutoff for CC SN progenitors at 40 Myr would be transformed to a soft decrease of the delay time distribution (DTD; SN rate as a function of the time after starburst) with a tail reaching ages up to 200 Myr. A clear detection of a CC SN progenitor in this age range confirming these predictions would produce a great impact in both the SN and stellar evolution communities.
On the other hand, stars with masses lower than 8 M⊙ evolve to form instead degenerate carbon-oxygen white dwarfs with masses in the range of 0.5-1.1 M⊙. If a white dwarf is in a binary system, it can accrete mass from the companion star and, under certain conditions, increase its mass to around 1.4 M⊙, the physical limit of electron pressure degeneracy. At that point thermonuclear reactions can ignite in its center to completely disrupt the star in a very bright thermonuclear explosion, called a type Ia SN. The exact understanding of the progenitor systems and explosion mechanism of SNe Ia remains elusive, and no direct progenitor detection has been reported yet. But there is growing evidence that the progenitor stars of SN Ia have wide range of ages following a DTD with a turn-on at around a few hundreds of Myr and a continuous decreasing rate from there to 11 Gyr. However, the turn-on age (i.e. the minimum age) at which stars can explode as SNe Ia have not been yet properly constrained. The detection of this cutoff would be of great impact in cosmology and in astrophysics in general.
Funded by the MSCA programme, the SNDTD project plans to go one step further and investigate these questions with the following goals: (i) constrain the shape of the late CC SN DTD tail; (ii) determine the lower turn-on age of the type Ia SN DTD; and (iii) test whether the star formation history (SFH) of stellar populations at SN Ia locations has any implication in its use as cosmological distance indicators.
