Final Report Summary - SPCND (Supernovae: Physics and Cosmology in the Next Decade)
Exploding stars, known as supernovae, impact upon many areas in astrophysics. They are particularly well-known for their key role in cosmology, leading to the discovery of the accelerating universe. Surprisingly, the supernovae that we use for this purpose, type la supernovae, suffer from a poor physical understanding, which in turn can limit their cosmological use. The SPCND project used major new astronomical surveys to improve our knowledge of supernova la astrophysics in order to make a new cosmological measurement, and explored the use of other types of supernovae in a cosmological setting. These new surveys used supernova spectra, and observed supernovae at wavelengths not before studied for large sample.
It is well known that type la supernovae are the thermonuclear explosions of white dwarf stars, and very likely live in binary systems (two stars orbiting each other in space). But a key question is whether type la supernovae originate from systems with two white dwarfs, or a white dwarf and a normal star. SPCND addressed this question using new data from the Public ESO Spectroscopic Survey of Transient Objects (PESSTO), and its newly-approved follow-on Large Programme, extended-PESSTO (e-PESSTO). These are major time allocations on Europe's best telescopes.
SPCND used data to examine the amount of material that surrounds the white dwarfs prior to explosion. This material, known as circumstellar material, can provide constraints on the nature and configuration of the star system that blew up. For example, the detection of hydrogen in such data (as detected by SPCND) would be indicative of the presence of a normal star as the companion to the white dwarf, as most normal stars are made of hydrogen. Our new data show that such systems do exist, and provide new constraints on their frequency. We also used data to examine the core of the supernova explosion, in order to see the types of elements synthesised in the thermonuclear explosion. This provided new constraints for models that attempt to explain their origin.
SPCND used data from the highly-successful Dark Energy Survey (DES) to investigate both dark energy and supernova astrophysics. We made the most robust measurement of dark energy to date using type Ia supernovae, and highlighted the key role that their host galaxies play in their cosmological use. We have unveiled new supernova types: long-lasting explosions that shine for many months and years, and core collapse supernovae that explode in the lowest metallicity environments in the universe. These have shown that supernovae are a far more diverse group of objects than previously imagined.
SPCND has also driven the creation of the VISTA Extragalactic Infrared Legacy Survey (VEILS), a major new European Southern Observatory public survey using the VISTA telescope. This is observed distant type la supernovae at infrared wavelengths, which are less susceptible to dust than traditional optical measures. This project also used data from DES.
Finally, a major focus of SPCND has been superluminous supernovae, a new type of supernova explosion some 50 times brighter than type la supernovae. Using data from DES, we assembled the largest dataset of distant superlumiunous supernovae, and used these data to investigate the physics of superluminous supernovae, and their use as cosmological standard candles (like type la supernovae). Their extreme brightness will allow them to be seen to much larger distances than type la supernovae, and thus opens up a new epoch of the universe's expansion history to study and measurement. We have made the first cosmological measurement using these objects and also learnt more about the nature of these enigmatic superluminous events: we have studied their early evolution to constrain the nature of the environments in which they explode.
It is well known that type la supernovae are the thermonuclear explosions of white dwarf stars, and very likely live in binary systems (two stars orbiting each other in space). But a key question is whether type la supernovae originate from systems with two white dwarfs, or a white dwarf and a normal star. SPCND addressed this question using new data from the Public ESO Spectroscopic Survey of Transient Objects (PESSTO), and its newly-approved follow-on Large Programme, extended-PESSTO (e-PESSTO). These are major time allocations on Europe's best telescopes.
SPCND used data to examine the amount of material that surrounds the white dwarfs prior to explosion. This material, known as circumstellar material, can provide constraints on the nature and configuration of the star system that blew up. For example, the detection of hydrogen in such data (as detected by SPCND) would be indicative of the presence of a normal star as the companion to the white dwarf, as most normal stars are made of hydrogen. Our new data show that such systems do exist, and provide new constraints on their frequency. We also used data to examine the core of the supernova explosion, in order to see the types of elements synthesised in the thermonuclear explosion. This provided new constraints for models that attempt to explain their origin.
SPCND used data from the highly-successful Dark Energy Survey (DES) to investigate both dark energy and supernova astrophysics. We made the most robust measurement of dark energy to date using type Ia supernovae, and highlighted the key role that their host galaxies play in their cosmological use. We have unveiled new supernova types: long-lasting explosions that shine for many months and years, and core collapse supernovae that explode in the lowest metallicity environments in the universe. These have shown that supernovae are a far more diverse group of objects than previously imagined.
SPCND has also driven the creation of the VISTA Extragalactic Infrared Legacy Survey (VEILS), a major new European Southern Observatory public survey using the VISTA telescope. This is observed distant type la supernovae at infrared wavelengths, which are less susceptible to dust than traditional optical measures. This project also used data from DES.
Finally, a major focus of SPCND has been superluminous supernovae, a new type of supernova explosion some 50 times brighter than type la supernovae. Using data from DES, we assembled the largest dataset of distant superlumiunous supernovae, and used these data to investigate the physics of superluminous supernovae, and their use as cosmological standard candles (like type la supernovae). Their extreme brightness will allow them to be seen to much larger distances than type la supernovae, and thus opens up a new epoch of the universe's expansion history to study and measurement. We have made the first cosmological measurement using these objects and also learnt more about the nature of these enigmatic superluminous events: we have studied their early evolution to constrain the nature of the environments in which they explode.