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Browsing by Subject "Spectroscopic observations"

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  • Damsted, Sanna (2020)
    Galaxy clusters are the largest tightly gravitationally bound structures in the Universe. They are abundant and uniformly distributed in the sky, which makes them excellent targets for studying the history and properties of our Universe. They can be used to study some of the burning questions in astrophysics and cosmology. For example, how have the large scale structures evolved from billions of years ago to how we see them today, and what are the best values for parameters like matter densities in our cosmological theories. Photometric galaxy cluster surveys have been conducted for decades, but now is the dawn of large scale spectroscopic surveys. Spectroscopy gives more precise redshift values for galaxies and galaxy clusters than photometric observations, which in turn makes other astrophysical parameters like mass estimation of galaxy clusters much more reliable. The SPIDERS galaxy cluster survey is the largest X-ray detected, spectroscopic, visually validated survey conducted to date. It improves the precision of galaxy cluster redshifts by a factor of 10. The precision of redshift has a direct improvement on other distance related parameters calculated by using galaxy clusters. The SPIDERS value added catalogue, which came out of the survey, is a tremendous achievement and will benefit astrophysicists and cosmologist around the world. The catalogue is the result of the work of the SPIDERS team of experts, and it is freely available online. This thesis explains how the SPIDERS survey was conducted; it’s phases, algorithms and the science behind it. I give many examples of the data processing and visual validation of targets, and explain the results and the significance of having such a large and precise data set.