Abstract

The statistics of galaxies observed by spectroscopic and imaging surveys are sensitive to the large-scale environment within which the galaxies formed. The “response” of galaxy properties to the presence of these “environments” is thus an important ingredient in the construction of theoretical models to explain the observed data. These “responses” can be measured in so-called Separate Universe simulations, in which the effect of long-wavelength perturbations on small-scale structure formation is mimicked by changing the cosmology (i.e., by going to a “separate universe”). In this talk, I will describe measurements of the responses of the total matter power spectrum and galaxy number counts (galaxy bias) carried out with Separate Universe simulations of the IllustrisTNG galaxy formation model. I will further show that these measurements allow one to calculate the impact that baryonic effects leave on higher-order correlation functions (including covariances), as well as to estimate galaxy bias parameters that are important to constrain inflation.