Periodic Reporting for period 1 - SNDTD (Resolving the origins of supernovae: constraining progenitors with integral field spectroscopy)
Reporting period: 2019-09-01 to 2021-08-31
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.
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.
For the correct development of the action a number of datasets are needed, basically consisting on integral field spectroscopy (IFS) of nearby SN host galaxies. These data have been collected basically from two sources: The PMAS/Ppak Integral-field Supernova hosts COmpilation (PISCO) is a project that use the PMAS integral field unit (IFU) mounted to the 3.5m telescope at the Calar Alto Observatory (CAHA). PISCO has been running as part of the SNDTD action and collected a total of 210 objects, which accounting for those previously available in CALIFA makes a total 367 SN hosts observed with PMAS. The All-weather MUse Supernova Integral-field Nearby Galaxies (AMUSING) survey share a similar aim than PISCO, but it is complementary because it focuses on objects in the Southern hemisphere by using MUSE, an IFU mounted to the 8.1m UT4 telescope at the Cerro Paranal Observatory. Observations run as part of the SNDTD action resulted in 202 galaxies contributing to the 689 finally collected in AMUSING. Each observation, once processed, results in a flux and wavelength calibrated 3D datacube (2 spatial + spectral dimensions) that can directly be used for science.
Our dataproducts have been used for different science purposes in more than 40 publications. In many cases we focused on analyzing single objects and provide a deep and extended context of the SN environments observed with IFS. We also performed analyses that required large statistical samples, either to study the environmental properties of SN host galaxies, or just studies focused on galaxies in general. Single galaxy in-depth studies (non SN related) were also performed. In some cases, the SN was still visible in our IFS data and some works used these nebular spectra. Related to the main objectives of the MSCA, we highlight the work published in Castrillo, A. et al., (2021, MNRAS 501 3122), where we presented a new approach to recover SN DTDs using a statistical analysis of a sample of 116 SNe in 102 galaxies. We evaluated different DTD models for different SN types, and found that the best DTD fit for SNe Ia was a power law with an exponent α=-1.1±0.3 and a cut-on time of Δ=50+100−35 Myr. For both CC SN types, we found a correlation with a Gaussian DTD model with widths of σ=82+129−23 Myr, for SNe II, and σ=56+141−9 Myr for SNe Ibc. This analysis demonstrated that IFS opens a new way of studying SN DTD models in the local Universe.
Our dataproducts have been used for different science purposes in more than 40 publications. In many cases we focused on analyzing single objects and provide a deep and extended context of the SN environments observed with IFS. We also performed analyses that required large statistical samples, either to study the environmental properties of SN host galaxies, or just studies focused on galaxies in general. Single galaxy in-depth studies (non SN related) were also performed. In some cases, the SN was still visible in our IFS data and some works used these nebular spectra. Related to the main objectives of the MSCA, we highlight the work published in Castrillo, A. et al., (2021, MNRAS 501 3122), where we presented a new approach to recover SN DTDs using a statistical analysis of a sample of 116 SNe in 102 galaxies. We evaluated different DTD models for different SN types, and found that the best DTD fit for SNe Ia was a power law with an exponent α=-1.1±0.3 and a cut-on time of Δ=50+100−35 Myr. For both CC SN types, we found a correlation with a Gaussian DTD model with widths of σ=82+129−23 Myr, for SNe II, and σ=56+141−9 Myr for SNe Ibc. This analysis demonstrated that IFS opens a new way of studying SN DTD models in the local Universe.
The full sample coming from PMAS is planned to be published with the accompanying paper on SNIa distances correlated to the local environmental parameters in the next couple of years. It will include the release of all PISCO cubes, and the 2D maps of all properties for all galaxies. Similarly, we plan to publish all MUSE datacubes and products with the AMUSING data release. This will include reduced ready-to-use 3D cubes of 689 SN host galaxies, corresponding to semesters P95 to P106, and all dataproducts described above. In the meanwhile, we published the extended sample, AMUSING plus other SN host galaxies and very nearby galaxies obtained from the ESO archive in López-Cobá, C. et al., (2020, AJ 159 167). After data releases, we will put all heavy files in a dedicated server at providing external access, and all 2D maps in a Zenodo repository, as we previously done for PISCO in Galbany et al. (2018). The final step of the MSCA will be the publication of the DTD analysis where, following the work presented in Castrillo et al. (2021), we will use IFS data of around thousand galaxies and this improved method to recover the star formation histories at every single observed position including the SN position, and use the method presented in Maoz et al. (2010) to recover the delay-time distribution (DTD) of both CC SN and SNe Ia. This will turn out to be the more complete, extended and in-depth statistical analysis of SN progenitors to date.