Speaker
Description
The new generation of galaxy surveys will reach an unprecedented precision, allowing to test cosmology and gravity theories from the relativistic effects on the clustering of matter in the universe. In particular, the magnification bias, the change of observed galaxy density caused by lensing magnification, can be used as a cosmological probe. In this work, we investigate the impact of the magnification bias within the w0wa-nu CDM cosmological framework using a suite of high-resolution N-body simulations. We explore the parameter space using a Latin Hypercube Sampling (LHS), and simulate 32 distinct cosmological models (with a planned extension to at least 64 models) where the different cosmological parameters are varied. Building on the work of Breton et al., 2019 and Rasera et al., 2022, we perform relativistic ray-tracing for each cosmology, to generate lightcone catalogs that include the relativistic effects on the matter distribution, and measure the full set of relativistic 3x2pt correlation functions (galaxy clustering, galaxy–galaxy lensing and cosmic shear). We can then compare the observables computed in the relativistic catalog to the same observables computed assuming the Born approximation, to isolate the effect of the magnification bias on these observables.
We then construct an emulator based on Gaussian Processes, trained on the measured correlation functions, to extrapolate the cosmological dependence of the amplitude of the magnification bias. Our emulator provides fast and accurate predictions of the relativistic corrections on the 3x2 pts correlation functions, and can be directly used to perform MCMC from correlation functions measured by observations. We show that the magnification bias induces measurable deviations in 3x2pt statistics, and that the relativistic correction to the galaxy-lensing correlation function is particularly sensitive to the dark energy equation of state. In future work, we plan to extend this analysis to additional observables, such as Minkowski functionals, and to broaden the cosmological framework to include models of modified gravity.