The upcoming radio telescope SKA is expected to detect the 21-cm signal from the cosmic dawn for the first time, allowing us to probe the astrophysical processes of this previously unobserved era. The 21-cm differential brightness temperature fluctuations from the cosmic dawn are predominantly due to early inhomogeneous heating of the neutral intergalactic medium and variations in Lyman-alpha photon density. Inhomogeneous heating is driven by high energy, X-ray photons which have long mean free paths and thus penetrate deep into the neutral IGM. On the other hand the Lyman-alpha fluctuations depend on the soft, UV radiation from these sources. I will present our large-volume (349,Mpc comoving) suite of fully numerical radiative transfer simulations of this epoch, with a boxsize big enough to make statistically meaningful predictions. The simulations include the effects of helium ionisation, secondary ionisations and multi-frequency photo-heating in order to include different types of X-ray sources (High mass X-ray binaries sources and QSO sources) in addition to black body stellar sources and Lyman-alpha fluctuations, which are added as a post-processing step.
Speaker: Hannah Ross, Lawrence Berkeley Lab
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