Probing cosmic large-scale structure beyond the average

IAP weekly specialised seminars / 29 November 2024
Cora Uhlemann (Univ. Bielefeld, Allemagne)
As galaxies form within the skeleton of dark matter, we can use large galaxy surveys as a laboratory for fundamental physics. The Euclid and Rubin LSST surveys will map the distribution of billions of galaxies across most of the sky and over 10 billion years of cosmic history. By identifying locations and shapes of galaxies, we can connect dark matter to galaxies and probe the rise of dark energy that determines the fate of our Universe. Analysing billions of galaxies across huge volumes is a big data challenge involving nonlinear physics, commonly tackled by only considering simple averages. I will describe how we can squeeze out more information by probing the large-scale structure beyond the average of standard forward models and statistical analyses. I will focus on methods to probe different density environments that are lumped together in traditional two-point statistics. This is particularly important for probing extensions of LCDM including massive neutrinos, dark matter, dynamical dark energy and modified gravity. I will demonstrate that one-point statistics give access to non-Gaussian information complementary to common two-point statistics. I will explain how the cosmology dependence of one-point probability distribution of dark matter densities can be predicted and translated to galaxy clustering and weak lensing and observables. I will give a glimpse into ongoing work to predict the one-point distributions of galaxy counts and the tomographic weak lensing signal.