Beschreibung
Baryon feedback in galaxy-galaxy lensing (GGL) and the combination with galaxy clustering and cosmic shear (3x2pt), and its measurement in hydrodynamical simulations, are much less studied than in cosmic shear alone. Modeling baryonic feedback with counterterms in the hybrid effective field theory (HEFT) has not been tested against realistic baryonic effects from simulations.
This project aims to study the sufficiency of the HEFT counterterm model in capturing baryonic physics, using measurements of its impact on the galaxy, galaxy-matter, and matter power spectra from hydrodynamical simulations for DESI-like galaxy samples. We will select DESI BGS- and LRG-like galaxies in the Magneticum Pathfinder simulation by applying stellar mass, SFR, and magnitude cuts to match the target number densities. The selected galaxies will be bijectively matched to subhalos in the dark-matter-only (DMO) runs. For galaxies without a bijective match, typically those affected by tidal stripping, we will reconstruct their DMO positions using their distances from the host halo center.
With the measured hydro-to-DMO ratios in the clustering, matter, and cross power spectra, we will perform simulated likelihood analysis to test up to what scale the counterterm model can account for the baryonic effects, and whether higher-order counterterms are required for galaxy-galaxy lensing. We will further investigate the relationship between counterterms in clustering, GGL, and cosmic shear, and the implications for their prior choices, which are currently treated as separate nuisance parameters with conservative priors.