Core-collapse supernovae (CCSNe) are huge explosions marking the end of very young, very massive (between 8 and 150 times the mass of the Sun) stars' lifetimes. These stars are sustained for millions of years by their own nuclear fuel, however, the more massive the star the more quickly it uses up this fuel. When this happens the star can no longer support itself against gravity and starts to collapse. The collapsing material falls into the centre, bounces off the dense core of the star and then begins to rebound, smashing into the material still falling into the centre and causing a huge explosion. This explosion is what we observe as a supernova and they are amongst the most luminous events in the Universe. The explosions also expel most of the stars material into the surrounding space, and this material is of critical importance to the Universe we observe today. All elements heavier than hydrogen, helium and lithium were produced inside stars, and these supernova explosions dispersed them throughout the Universe, providing the material for the next generation of stars, planets and life. So the carbon, nitrogen, and oxygen which makes up our bodies comes from the centres of stars - we are all stardust!
Despite the importance of these objects, there are still large gaps in our knowledge of the processes involved in producing these massive stars and, indeed, exactly which stars create the different types of supernovae we observe today. The study of CCSNe can also lead to a deeper understanding of galactic evolution as they trace the young stellar populations within systems. My research aims to constrain the different types of stars producing supernovae by looking at the local environments from which they arise within their specific host galaxy. Although this is not as ideal as physically observing the star prior to explosion, it can be achieved with a much larger proportion of CCSNe. Even with Hubble Space Telescope pre-explosion imaging of very-nearby galaxies such as the one shown above, it is tremendously difficult to pinpoint the star, or group of stars which may have produced the supernova. By looking at the local environment we can gather a lot of information on the types and masses of stars in that region and the elements which make them up.
Most of my work to date has been related to looking at the local environments of CCSNe in galaxies which are undergoing collisions or interactions with other galaxies, compared to those in "normal" systems. This lead to a surprising and somewhat remarkable result. In interacting systems the supernovae are more centrally located than in normal spiral galaxies. Not only this but the types of supernovae seen in the most central regions of the interacting galaxies come from arguably more massive stars. This means that within the central regions of merging galaxies a different type of star formation process is taking place to else where in the Universe! For more details on this result please see the publications links to Habergham et al. 2010, and 2012 and the Astronomy Now Article .
My other work probes this result further by measuring the chemical content of the gaseous regions around the supernova explosion sites and throughout the host galaxies as a whole, and to expand the sample of supernovae used in the analysis by exploring large databases of galaxies and using the trends seen to predict future sites of CCSNe. I am also working on specific, rare, supernovae types to try and place constraints upon the star formation history of the environments in which they are found. As an observational astronomer I utilise telescopes to which the UK has access. For my research the Isaac Newton Telescope, William Herschel Telescope and the The Liverpool Telescope on La Palma, (operated respectively by the Isaac Newton Group and Liverpool John Moores University respectively, in the spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias) have been invaluable. Long-live the UK's involvement in observational facilities around the world!
Stritzinger, Taddia, Fransson, Fox, Morrell, Phillips, Sollerman, Anderson, Boldt, Brown, Campillay, Castellon, Contreras, Folatelli, Habergham, Hamuy, Hjorth, James, Krzeminski, Mattila, Persson, and Roth, 2012, ApJ, 756, 173