Abstract
The central focus of contemporary cosmological research lies in interpreting the distribution and properties of the different components of the Universe, understanding their formation and evolution. In the framework of the Lambda Cold Dark Matter paradigm, which describes the Universe with three primary constituents—dark energy, dark matter, and ordinary matter— tiny density fluctuations rise and grow in the early Universe under the influence of gravity, to create the massive, dark matter dominated structures we observe today. Over the course of this evolution, dark matter halos serve as gravitational potential wells, attracting ordinary baryonic matter that undergoes a series of physical transformations. Therefore, mapping the distribution of baryons, from galaxy clusters to larger-scale structures, is crucial for comprehending the growth and evolution of all components of the Universe. My research is centered on mapping the baryonic content within both galaxy clusters and larger filaments filling the Universe, using the Fourier analysis. Through this technique I can cross-correlate the hot X-ray emitting gas and dark matter distribution, reconstructed with gravitational lensing, assessing how well the two components trace each other. The results of this investigation have fundamental cosmological implications. With a similar approach, I adopted the power spectrum analysis to isolate the contribution of the warm hot intergalactic medium to the cosmic X-ray background, the diffuse glow of X-ray radiation that appears to fill the Universe uniformly in all directions. The warm hot intergalactic medium is a warm-to-hot plasma that fills the spaces between galaxies. The study of this elusive component is fundamental to solve what is known as ”missing baryon problem”, where the observed amount of baryonic matter does not match theoretical predictions from cosmology.