In this thesis, the research focuses on the properties of dark matter and dark matter haloes and how they connect with the galaxies we can observe in the Universe. Because of the still unknown... Show moreIn this thesis, the research focuses on the properties of dark matter and dark matter haloes and how they connect with the galaxies we can observe in the Universe. Because of the still unknown nature of dark matter, we tend to study it using the properties of its distribution and its properties on galactic scales and beyond. The galaxy–dark matter connection is important for three main reasons, and understanding it helps with answering the largest questions in astrophysics and cosmology today. First question includes the understanding of the physics of galaxy formation. Secondly, the inference of cosmological parameters – if we want to robustly measure the cosmological parameters, we have to understand, how the galaxies interplay with the dark matter, and thirdly, the inference of evolution of matter distribution and properties of dark matter. We explore different aspects of the galaxy–dark matter connection that can be measured using gravitational lensing, more specifically, using galaxy-galaxy lensing as our primary probe. We use the halo model together with the halo occupation distributions to statistically describe the galaxy-halo connection and to constrain assembly bias in rich galaxy groups. The same theoretical framework is also used to constrain the nature of galaxy bias. Show less
Galaxies form and evolve through close interaction with their surroundings. As a result, the heavy elements ('metals') that are synthesized in stars, are found both inside and outside galaxies.... Show moreGalaxies form and evolve through close interaction with their surroundings. As a result, the heavy elements ('metals') that are synthesized in stars, are found both inside and outside galaxies. They trace the gas returned by stars, while providing information on the time-scales and physical conditions characterizing various stages of galaxy evolution through their elemental composition and ionization state. In this thesis, we explore what metals can tell us about galaxy formation. We complement theoretical work using the EAGLE simulations, where we focus on the galaxies as well as the surrounding medium, with an observational study of the low-redshift (z < 1) circumgalactic medium using the MUSE instrument on the VLT. Show less
