Cosmological Surveys

Members: David Alonso, Pedro G. Ferreira and Lance Miller

Cosmology has made gigantic steps in the last 3 decades, transitioning from a mostly speculative “order of magnitude” science into a robust discipline able to make predictions and measurement at the percent level. This progress has been the fruit of important developments in theory and data analysis methods, accompanied by a rapid growth in the quantity, quality and variety of astronomical observations of cosmological relevance.

At Oxford, we are deeply involved in several of these cosmological experiments. We have made important contributions to ongoing optical and radio galaxy surveys, such as the extended Baryon Oscillation Spectroscopic Survey (eBOSS), the Kilo-Degree Survey (KiDS), and the LOFAR Two-metre Sky Survey (LoTSS). These experiments track the evolution of the Universe's large scale structure through the spatial distribution of galaxies, as well as from the deformation in their observed shapes caused by the gravitational lensing effect. These data allow us to track the evolution of matter fluctuations and the Universe's geometry across cosmic time, and to study the impact of Dark Energy and Dark Matter on this evolution. We are also strongly involved in the next generation of optical surveys, which will soon start covering tremendous swathes of the Universe with an unprecedented sensitivity. These include the Legacy Survey of Space and Time (LSST) at the Vera C. Rubin Observatory, and the Euclid satellite mission.

We also have a strong track record in the study of the Cosmic Microwave Background (CMB): the first photons that were able to travel freely after the Big-Bang. The CMB is one of the cleanest cosmological probe, providing us with an exquisite picture of the early Universe, and allowing us to place strong constraints on its dominant energy components and the properties of the initial density fluctuations. The propagation of the CMB photons is also affected by the late-time large-scale structure via gravitational lensing and their interaction with the hot inter-galactic medium. Thus, CMB data is also able to provide invaluable information on the more recent evolution of the Universe. In this context, we have played an important role in past missions such as Planck, ongoing experiments such the Atacama Cosmology Telescope (ACT), and near-future facilities such as the Simons Observatory (SO).

Our involvement in these experiments also allows us to exploit the unique information that arises from the combination of CMB and galaxy survey data, which is significantly larger than the sum of their parts.