Oral Presentation

Birth of Earliest Warm-Hot Intergalactic Medium in a Protocluster at z=2.3

Author(s): Chenze Dong (Kavli IPMU)

Presenter: Chenze Dong (Kavli IPMU)

The observation of the local universe reveals a 30~40% deficit of baryon matter compared with the prediction of the standard model, commonly known as the "Missing Baryon Problem." The hard-to-detect nature of the warm-hot intergalactic medium (WHIM) may contribute to the missing baryon budget. According to the cosmological simulations, the WHIM with a temperature higher than 100,000 Kelvin and low density may spam throughout the universe but is almost invisible in the observation. Due to a lack of efficient tracers, there is little evidence of the production and evolution of WHIM, especially at high redshift.
In this talk, we first present our discovery on a protocluster at z=2.3 named COSTCO-I. The protocluster, firstly identified via the galaxy surveys, was later found corresponding to a region with high transmission in CLAMATO Lyman-alpha tomography map, contrary to the theoretical relation where protoclusters would have low Lyman-alpha transmission (Flatuation Gunner-Peterson Approximation, FGPA). We attributed this to a hotter intergalactic medium (IGM) across a few physical megaparsecs around the protocluster, implying the formation of WHIM associated with the protocluster. After that, we introduce our recent progress on constraining the mechanism of large-scale heating with The Three Hundred simulation suites. We found that the simulation prescription with AGN kinetic feedback matched the COSTCO-I well on the overdensity-transmission parameter space, contrary to the rest prescriptions with weaker AGN feedback or stellar-only feedback exhibited a lower Lyman-alpha transmission. We thus argue jet feedback is a plausible candidate for the large-scale gas heating around COSTCO-I, rather than stellar feedback or gravitational shock heating.
In the future, the prime focus spectroscopy (PFS) on the Subaru Telescope will profoundly extend the mapping volume of tomography survey to about 100 times more than CLAMATO. We expect to discover more protoclusters like COSTCO-I around z~2, which will shed light on the origin of WHIM associated with structures at cosmic noon.