Fast Hydro Simulation for the Intracluster Medium Physics and Cosmology with the Sunyaev-Zel’dovich Effect

My thesis focuses on developing a cosmological code based on an innovative hydroparticle-mesh (HPM) algorithm for Efficient and Rapid (HYPER) simulations of gas

and dark matter (He et al., 2021b). HYPER can produce lightcone catalogs of dark matter halos and full-sky tomographic maps of the lensing convergence, Sunyaev-

Zel'dovich (SZ) effect and X-ray emission. These simulation products are useful for testing data analysis pipelines, generating training data for machine learning, understanding selection and systematic effects, and interpreting astrophysical and cosmological constraints. I start my thesis by presenting our study on an analytical model for the average cluster pressure profile, which we use to implement the HYPER simulation. We first come up with a model for estimating hydrostatic bias in the Xray measurement by fitting a power-law to the relation between the \true" halo mass and X-ray cluster mass in hydrodynamic simulations (IllustrisTNG, BAHAMAS, and MACSIS). We apply this model to the REXCESS X-ray cluster sample and adjust the

Universal Pressure Profile (UPP) derived from scaled and stacked pressure profiles (Arnaud et al., 2010) for the hydrostatic mass bias. Our work eventually leads to

an updated model, Debiased Pressure Profile (DPP), for the gas pressure profile of galaxy clusters (He et al., 2021a). The second part of this thesis introduces HYPER code in detail, which updates the HPM approach of (Gnedin & Hui, 1998) to expand the scope of its application from the lower-density intergalactic medium (IGM) to the higher-density intracluster medium (ICM). In order to achieve high efficiency and high fidelity for the approximate hydrodynamic solver, the pressure term in the gas equations of motion is calculated using robust physical models. In particular,

we use the dark matter halo model, ICM pressure profile, and IGM temperature density relation to model the gas physics in the IGM and ICM regime, all of which can be systematically varied for parameter-space studies. We show that the HYPER simulation results are in good agreement with the halo model expectations. At the end of this part, we also envision the perspective of use cases for HYPER. I discuss the application of HYPER simulation in SZ science in the final part of this dissertation. We present a template for calculating the thermal and kinetic angular power spectra

using the outputs of HYPER simulations, which can be applied to the analyses for future SZ surveys. We also show a simplified case in which this template is combined with observation data to constrain cosmological parameters.