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 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.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- May 2021
- DOI:
- 10.1093/mnras/stab776
- arXiv:
- arXiv:2103.07483
- Bibcode:
- 2021MNRAS.503.4551G
- Keywords:
-
- radiative transfer;
- galaxies: formation;
- intergalactic medium;
- cosmology: theory;
- dark ages;
- reionization;
- first stars;
- X-rays: galaxies;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- 13 Pages, 6 Figures, 5 Tables, Accepted for publication in MNRAS