Speaker
Description
Primordial non-Gaussianities (PNG), parameterized by the amplitude fNL, provide a direct window into the physics of the early Universe and a means to discriminate among inflationary models. Constraints on fNL from the cosmic microwave background are limited by cosmic variance, making large-scale structure surveys such as DESI a promising avenue for further progress. A central challenge is that the PNG signal is degenerate with the galaxy bias parameter bϕ, which quantifies the response of galaxy clustering to PNG. Therefore, tight priors on bϕ are required to break this degeneracy.
In this work, we present estimates of priors on bϕ for the second DESI data release using semi-analytical models of galaxy formation (SAMs). We construct galaxy samples with a range of properties and use these to select DESI-like samples of luminous red galaxies (LRGs), emission-line galaxies (ELGs), and quasars (QSOs). We perform our analysis using two independent semi-analytical models, SHARK and GALFORM, as well as two independent methodologies to estimate bϕ. We find good agreement between the methodologies.
However, we find that the predicted values of bϕ depend sensitively on the underlying galaxy physics implemented in the semi-analytical models.