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AR 14314 (Archival Research)

Mon Jul 15 04:42:46 GMT 2024

Principal Investigator: J. Shull
PI Institution: University of Colorado at Boulder
Investigators (xml)

Title: Spatial Modeling of the Topology of He II Reionization
Cycle: 23

Abstract
The reionization of He II near redshift z = 3 marks the last major phase change in the intergalactic medium. Spatially rare quasars, with their harder UV spectra, are expected to be the primary sources for He II reionization. Our HST-AR-Theory project will use the Eulerian N-body + hydrodynamics code Enzo to simulate the topology, physical conditions, and evolution of the He II reionization epoch. Our important new modeling advance is to insert discrete photoionizing sources and perform radiative transfer using the flux-limited diffusion module. Properties of He II in the IGM and in QSO proximity zones can now be constrained spectroscopically by the Cosmic Origins Spectrograph: time evolution of the global He II and He III fractions and inhomogeneity of ionized regions in the IGM and around QSOs. We will compare synthetic quasar sightlines to existing observations, study the quasar population responsible for He II reionization, and investigate the impact of QSO lifetimes, luminosity functions, and other parameters that are consistent with current observations.