Probing Baryonic Matter in the Universe with the Sunyaev-Zel’dovich Effect

Speaker: Henry Liu (UC Berkeley) In Person and zoom 

Zoom info: https://stanford.zoom.us/my/sihanyuan?pwd=QnpsUHZWWGJ2ekVYWmZVL3BmM0gzZ…

Baryons constitute approximately 5% of the universe's total energy density, yet observations of visible matter—such as stars and galaxies—account for only a fraction of the expected baryon mass. A significant portion is thought to reside in the warm-hot intergalactic medium (WHIM). In this talk, I will present two projects that probe baryon distribution using the Sunyaev-Zel’dovich (SZ) effects. The first project cross-correlates galaxies from the Dark Energy Spectroscopic Instrument (DESI) with cosmic microwave background (CMB) maps from the Atacama Cosmology Telescope to measure the thermal SZ (tSZ) effect, achieving a high signal-to-noise ratio. The second project reconstructs simulated fields of the thermal and kinematic SZ (kSZ) effects, comparing two approaches—Gaussian process emulators and Hybrid Effective Field Theory—for inferring baryonic effects from dark matter N-body simulations. Finally, I will discuss the broader implications of these studies for our understanding of cosmic baryons and outline future research directions.