Speaker
Description
Stage-IV surveys like DESI increasingly rely on z > 1 Emission-Line Galaxies (ELGs) for cross-correlation analyses, capitalizing on their overlap with CMB secondaries such as the CMB lensing and Cosmic Infrared Background (CIB) kernels. However, unlocking their full cosmological potential requires navigating complex observational systematics and non-trivial galaxy-halo connections. In this talk, I will present a comprehensive framework bridging recent observational constraints with rigorous methodological development. First, I will present cross-correlation measurements between the DESI ELG photometric sample and Planck CMB lensing and CIB maps. After detailing our mitigation of key observational systematics—notably Milky Way extinction—I will discuss the resulting physical implications. These include exploring the Omega_M - sigma_8 parameter space to probe current LCDM tensions, and revealing insights into galaxy evolution, such as elevated star-formation efficiencies and extended ELG halo profiles. Motivated by the systematics uncovered in this photometric data, I will then demonstrate how we are preparing for the spectroscopic era by evaluating the sensitivity of the cross-correlation power spectrum, Ckg, to ELG-halo connection choices. By stress-testing the DESI DR2 inference pipeline with expressive HOD models and Hybrid Effective Field Theory, I will quantify the associated systematic budgets and introduce a new suite of public mock catalogs designed for community pipeline validation.