Title: Challenges and Opportunities of Galaxy Redshift Surveys

Speaker: Dr. Shadab Alam

Affiliation: Institute for Astronomy, University of Edinburgh, UK

Abstract: The initial metric perturbations in the universe were small O(10^-5) allowing linearised equations to give a very good description of the evolution of the Universe. The standard (LCDM) model predicts the evolution of the clustering statistics (e.g. P(k)) of the matter distribution. Under the simplified assumption, all the complex physics of galaxy formation is encompassed in few parameters called the galaxy biases. We know that these assumptions fail as we approach scales equivalent to the size of a galaxy. While such solutions were appropriate for the past experiments, (e.g: SDSS) the measurement precision of ongoing experiments (e.g: DESI, EUCLID, 4MOST, PFS, LSST) is going to be improved by an order of magnitude. Therefore, one of the challenge is to understand the limits of the current models to a precision better than ongoing experiments to avoid biases in interpreting the underlying physics of the universe. This is challenging because of two reasons: first the growth of density perturbations and its coupling to the velocity field becomes highly non-linear and second, high precision true predictions requires solving the physics of galaxy formation. At the same time there is a golden opportunity to improve upon the models by identifying the dominant failure modes. I will describe current state of art results from Large Scale Structure (LSS) and my efforts to validate and improve the theoretical models specially focusing on the redshift space distortions and its implications on our ability to derive galaxy physics and cosmology from ongoing experiments.