Preparing for and making cosmological measurements from galaxy surveys

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Research over the last 50 years has provided a tremendous insight into the Universe, with many of the key parameters determined such as the age of the Universe and the split of energy-density components. Surprisingly, this has thrown up some big questions: we don't know what the dominant constituents of the Universe are made of, or why the expansion is accelerating. Thankfully, we are in a golden era of experimental data in cosmology, and the period 2019-2024 will be an extremely important one for cosmology with galaxy surveys spearheading exciting experimental advances. The proposed programme of research will prepare for and exploit the data from the Euclid satellite mission to understand the physical mechanism that is causing the accelerated expansion of the Universe, commonly termed Dark Energy. The students supported by this grant will develop and apply the techniques required to make cosmological measurements using data from the international Euclid satellite mission. Dr Percival has a number of senior scientific management positions in the Euclid Consortium ensuring that the work concentrates on the critical developments that are required. Euclid will create a survey of the Universe at a level that is an order of magnitude improvement over current data. As it is scheduled to launch in 2022, the initial work will concentrate on preparing for this mission, before focus shifts to analysing the first data towards the end of the timeline covered by this application. The intention with this proposal is to set up a core group of scientists undertaking this research within Canada, which will continue to the generation of surveys to come after Euclid: including the Large Synoptic Survey Telescope (LSST) and the Maunakea Spectroscopic Explorer (MSE). Alongside implementing and optimising known methods for making cosmological measurements based on the clustering of galaxies, we will consider more novel techniques. Using a recently developed model for the velocities of galaxies around voids, the team will investigate whether we can make robust projection-based measurements to measure cosmological expansion with voids. Voids are regions with very few galaxies, and have some very attractive properties that make modelling simple, such as the linear motions of galaxies within them. Ultimately, our ambition is to find a deviation from the concordance model based on Einstein's cosmology constant driving Dark Energy. Such a discovery would lead to a fundamental change in our understanding of the Universe. In the event that we do not find such a deviation, the research will have improved our understanding of cosmology, developed new statistic tools of universal interest, trained a number of students, and placed Canada at the forefront of a very exciting field in physics. In particular, the skills developed by the students developing and applying novel statistical techniques, will be useful both within and outside of academia.