A unified approach to the study of dark matter and baryons in the large scale structure of the Universe

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The study of the universe is stumbling upon two mysteries : it is made for 5% of normal matter, 20% of an unknown type of matter, dark matter, and for 75% of a puzzling form of energy, dark energy. A worldwide quest is underway to probe, map and explain those dark components. In the past ten years, a dozen of international teams organized mega surveys involving the largest ground based telescopes and state of the art satellites, and developed ground breaking computing techniques to analyse thousands of terabytes of data. Gravitational lensing is the tool of choice to reveal the presence of dark matter. According the Einstein's general theory of relativity, light from distant galaxies is distorted by massive astronomical bodies present between the source and the observer. This property can be used to weigh and map matter that cannot be detected by any other means. Fifteen years ago, L. Van Waerbeke was among the pioneers who laid the theoretical and observational foundations of this new field of research. By statistically analyzing the distorted shapes of millions of background galaxies, he performed the first detection of gravitational lensing by a large scale structure. Today, gravitational lensing is leading the science in several international satellite projects like Wide Field Infrared Survey Telescope in the US and Euclid in Europe. For the past five years, L. Van Waerbeke has led an international team, CFHTLenS, who brought gravitational lensing to a new level of precision and reliability. Analyzing 4 TB of data, CFHTLenS provided the first large scale map of dark matter, which in turn provides clues about how galaxies formed and how dark matter evolved in their halos. In 2013 alone, CFHTLens papers received more than 190 citations. The team made their highly processed data publicly available at the Canada Astronomy Data Centre and received 200,000 hits in the first twelve months. For the past twenty years, the Big Bang theory has been confirmed by a large body of evidence, like the famous observations of the cosmic microwave background radiation (CMB), but some gaps persist. Three and a half billion years into the history of the universe, 50% of protons and electrons became invisible to astronomers; for the past fifteen years, these “missing baryons” have been searched by X-ray and microwave satellites. In 2013, L. Van Waerbeke showed that gravitational lensing combined with CMB observations can detect the presence of missing baryons, opening the door to a new field of research that could measure their temperature and density, explore how they are recycled in stars, and bring a new confirmation of the Big Bang theory, and shed a new light on structure formation. Gravitational lensing data could also be cross correlated (GLx) with other mega surveys to probe the physics of baryons. In the five coming years, L Van Waerbeke will train a team of two postdoctoral fellows and four graduate students, and at least five undergraduate students, to develop new computing tools and simulations in order to become the leading team in GLx. The two known types of matter, baryons and dark matter, are intertwined, and L. Van Waerbeke believe that it is time to build models combining them together. In the coming decade, ever larger surveys will be undertaken, covering the entire sky. Dark matter and baryons in all possible stated will be mapped. L. Van Waerbeke wants to lay the theoretical and practical foundations to efficiently analyze this massive influx of data. Personnel trained in his team will export this expertise worldwide. In the near future, he expects this field of research to have far reaching applications, like measuring the mass of the elusive neutrino particles and refining Einstein's theory of gravity.