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Understanding the dark Universe with observational cosmology

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If you have a question about this talk, please contact David Stefanyszyn.

Cosmology is a new and fast growing field, owing this growth to both new technology and statistical methods in imaging and data processing. It is believed that we can explain the cosmology of the entire Universe using a handful of parameters through the standard cosmological model. This model has been very successful in predicting the distribution of galaxies and matter, as well as very early measurements of cosmic microwave background radiation. As the volume of data is growing we are starting to see cracks in this simple picture of the Universe, through tensions between the results of different observational analyses.

In this talk I will focus on the analysis of the data from the kilo degree survey (KiDS). KiDS is a purpose-built gravitational lensing survey with high quality images and a wide photometric coverage, resulting in very high fidelity data. This dataset, therefore, provides an excellent playground where we can test our methods in preparation for future weak lensing surveys. Already the first 450 degrees of the KiDS data shows a mild tension with CMB results from the Planck satellite, which has sparked both skepticism and excitement within the community. I will go through the systematics that can affect the results and methods to mitigate them. I will also show results from the combination of KiDS and the dark energy survey (DES). Combining probes of cosmology can break degeneracies in the parameter space, resulting in tighter constraints. I will finally show results for the combination of KiDS with spectroscopic galaxy surveys.

This talk is part of the Cosmology Lunch series.

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