Speaker
Description
Galaxies, as tracers of the large-scale structure of the Universe, are key observables for testing cosmological models in the late Universe and into the non-linear regime. In this context, multi-scale baryonic dynamics, and their evolution over time, can have considerable effects on the galaxy-halo connection. If unmodelled, residual uncertainties in the galaxy field can obstruct cosmological inference and weaken tests of extensions to ΛCDM. In two-dimensional projection along the line-of-sight, the relevant halo-level information can be incomplete or effectively marginalised over.
To this end, I will present an analytic galaxy bias model in projection that incorporates stochasticity and non-locality already at linear order, while enforcing physicality. I will show how the model can be calibrated to the projected power spectrum measured in hydrodynamical simulations to sample galaxy populations from simulated matter fields while conditioning on selected galaxy properties. The model matches the two-point statistics down to the simulations’ resolution by construction, while recovering the bispectrum down to ~10 Mpc up to z=3. The model better reproduces non-linearities driven by correlations between the local amplitude of the galaxy field and its phase, as well as the field’s mode coupling, than a local bias model across most scales and down to low halo masses. This improves the robustness of joint clustering plus galaxy-galaxy lensing consistency tests of the growth of structure, helping to separate astrophysical systematics from genuine scale-dependent structure growth. Finally, I will demonstrate how this framework enables efficient field-level forward modelling of galaxy positions consistent with hydrodynamical simulations, providing a practical route towards simulation-based inference and principled model comparison wit surveys such as Euclid and Rubin LSST.