07 June 2022Séminaire – Adélie Gorce (McGill)

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A global picture of the epoch of reionisation

Abstract

About a million years after the Big Bang, the Epoch of Reionisation sees the first light sources in the Universe slowly ionise the atoms of the surrounding IGM. Learning about this distant epoch has the potential of unveiling crucial information about the formation of the objects that sourced it: the first stars, galaxies, and early black holes. However, its observation remains elusive. Attempted measurements of the 21cm signal, coming directly from the high redshift neutral hydrogen, are still plagued with systematics, and modelling uncertainties prevent us from disentangling the reionisation signatures within astrophysical and cosmological data sets. In this talk, I will present the efforts that I have contributed to in the analysis, modelling and interpretation of both small-scale CMB observations and radio interferometric data to overcome these obstacles. I will focus on the results from the Hydrogen Epoch of Reionisation Array (HERA), which has recently given the lowest upper limits on the 21cm power spectrum at redshifts z > 7. I will then argue the potential of cross correlations, especially of CMB and 21cm signal observations, to give a coherent and accurate picture of reionisation.