Modelling the Intergalactic Baryons using Hydrodynamical Simulations

Abstract

One of the foremost problems of modern cosmology is the discrepancy between the predicted and observed baryon density, termed the "missing baryon problem". Recent developments in knowledge of cosmological large-scale structure have identified filaments, containing gas belonging the warm-hot intergalactic medium (WHIM), as a potential reservoir for the missing baryons. This phase is often not directly detectable due to its diffuse nature, however detections by means of inverse Comptonization due to the thermal Sunyaev-Zel'dovich effect on CMB photons have been performed. In this thesis, the EAGLE suite of cosmological simulations is used to perform an analysis of filament material joining neighbouring central galaxies. A stacking process to overcome low signal from individual pairs is laid out, and the Comptonization signal y from the averaged pair stack is measured, finding a y-excess of y_filament = (1.299 +/- 0.014) x 10^(-9). In comparing this measurement to recent observational results, I conclude that the excess is statistically significant and indicative of a contribution to the baryon density from WHIM filaments, and set out the direction of further research to better establish the nature of this contribution.

Date of Award	1 Aug 2021
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Scott Kay (Supervisor) & Michael Brown (Supervisor)