Abstract
ABSTRACT High-redshift 21-cm observations will provide crucial insights into the physical processes of the Epoch of Reionization. Next-generation interferometers such as the Square Kilometer Array will have enough sensitivity to directly image the 21-cm fluctuations and trace the evolution of the ionizing fronts. In this work, we develop an inferential approach to recover the sources and IGM properties of the process of reionization using the number and, in particular, the morphological pattern spectra of the ionized regions extracted from realistic mock observations. To do so, we extend the Markov Chain Monte Carlo analysis tool 21cmmc by including these 21-cm tomographic statistics and compare this method to only using the power spectrum. We demonstrate that the evolution of the number-count and morphology of the ionized regions as a function of redshift provides independent information to disentangle multiple reionization scenarios because it probes the average ionizing budget per baryon. Although less precise, we find that constraints inferred using 21-cm tomographic statistics are more robust to the presence of contaminants such as foreground residuals. This work highlights that combining power spectrum and tomographic analyses more accurately recovers the astrophysics of reionization.
Highlights
The formation of the first stars and galaxies through gravitational instability of small density fluctuations, several hundred million years after recombination, marks the beginning of a key phase transition in the Universe history referred to as the Cosmic Dawn
While this might question the use of these statistics to infer the astrophysics of reionization, we show in Section 6.4 that 21-cm tomographic statistics are more robust to the presence of residual artefacts in the observation
We have examined the use of statistics extracted from 21-cm tomographic images to constrain the properties of the reionization sources using a Bayesian statistical inference framework
Summary
The formation of the first stars and galaxies through gravitational instability of small density fluctuations, several hundred million years after recombination, marks the beginning of a key phase transition in the Universe history referred to as the Cosmic Dawn. These first light sources emitted photons with enough energy to ionize the neutral hydrogen, which propagated in the intergalactic medium (IGM) and progressively reionized the entire Universe. This latter era is called the Epoch of Reionization (EoR), where the transition from the Cosmic Dawn is rather ill defined Indirect proxies are needed to estimate the ionizing efficiency of the sources of reionization, and some progress has been recently made in that direction using analogues at lower redshift (e.g. Schaerer et al 2016; Verhamme et al 2017; Chisholm et al 2018, 2020; Henry et al 2018; Gazagnes et al 2018, 2020; Wang et al 2019; Cen 2020; Izotov et al 2020)
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