Resumen de Cosmology and the galaxy-matter connection using weak gravitational lensing cross-correlations in the dark energy survey
In this thesis we use data from the Dark Energy Survey to study the evolution and contents of the Universe. The Dark Energy Survey (DES) has built a map of galaxies covering one eighth of the southern sky, measuring the positions and distances to hundreds of millions of galaxies, with the main goal to shed light on the reasons behind the observationally-confirmed accelerated expansion of the Universe. The mechanisms that could drive this accelerated expansion include some vacuum energy associated with the cosmological constant, another form of dark energy, or a modification of General Relativity. With galaxy surveys such as DES we aim to distinguish between these possibilities by probing the growth of structure and geometry of the Universe as a function of time.
In this thesis we use weak gravitational lensing measurements from the Dark Energy Survey to contribute to this final goal. Gravitational lensing is produced when light from background objects is deflected due to some foreground mass distribution that curves the space-time canvas. In particular, weak gravitational lensing, which can only be measured in a statistical manner, has emerged as one of the most powerful probes of cosmology, being sensitive to both the geometry of the Universe and the history of structure growth, and is the main technique used in this thesis. Specifically, we have used cross-correlations between a background source of light, such as distant galaxies or the Cosmic Microwave Background (CMB), and galaxy positions in the foreground, tracing the Large-Scale Structure producing the lensing. On one hand, we have used these weak lensing cross-correlations sensitivity to the history of growth of structure and to the geometry of the Universe, to constrain cosmological parameters in combination with other probes. On the other hand, since lensing cross-correlations are also sensitive to the relation between the baryonic (visible) matter forming galaxies and the underlying (mostly dark) matter field, we have been able to measure the so-called galaxy bias, which encapsulates this relation between galaxies and matter.
