Constraining the state of the intergalactic medium during the Epoch of Reionization using MWA 21-cm signal observations
ABSTRACT The Murchison Widefield Array (MWA) team has derived new upper limits on the spherically averaged power spectrum of the 21-cm signal at six redshifts in the range z ≈ 6.5–8.7. We use these upper limits and a Bayesian inference framework to derive constraints on the ionization and thermal st...
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Veröffentlicht in: | Monthly notices of the Royal Astronomical Society 2021-05, Vol.503 (3), p.4551-4562 |
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The Murchison Widefield Array (MWA) team has derived new upper limits on the spherically averaged power spectrum of the 21-cm signal at six redshifts in the range z ≈ 6.5–8.7. We use these upper limits and a Bayesian inference framework to derive constraints on the ionization and thermal state of the intergalactic medium (IGM) as well as on the strength of a possible additional radio background. We do not find any constraints on the state of the IGM for z ≳ 7.8 if no additional radio background is present. In the presence of such a radio background, the 95 per cent credible intervals of the disfavoured models at redshift ≳ 6.5 correspond to an IGM with a volume-averaged fraction of ionized regions below 0.6 and an average gas temperature ≲ 103 K. In these models, the heated regions are characterized by a temperature larger than that of the radio background, and by a distribution with characteristic size $\lesssim 10\, h^{-1}$ Mpc and a full width at half maximum (FWHM) of $\lesssim 30\, h^{-1}$ Mpc. Within the same credible interval limits, we exclude an additional radio background of at least $0.008{{\ \rm per\ cent}}$ of the CMB at 1.42 GHz. |
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ISSN: | 0035-8711 1365-2966 1365-2966 |
DOI: | 10.1093/mnras/stab776 |