Neutral island statistics during reionization from 21-cm tomography

Giri, S K, Mellema, G, Aldheimer, T, Dixon, Keri L and Iliev, Ilian T (2019) Neutral island statistics during reionization from 21-cm tomography. Monthly Notices of the Royal Astronomical Society, 489 (2). pp. 1590-1605. ISSN 0035-8711

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Abstract

We present the prospects of extracting information about the epoch of reionization by identifying the remaining neutral regions, referred to as islands, in tomographic observations of the redshifted 21-cm signal. Using simulated data sets we show that at late times the 21-cm power spectrum is fairly insensitive to the details of the reionization process but that the properties of the neutral islands can distinguish between different reionization scenarios. We compare the properties of these islands with those of ionized bubbles. At equivalent volumefilling
fractions, neutral islands tend to be fewer in number but larger compared to the ionized bubbles. In addition, the evolution of the size distribution of neutral islands is found to be slower than that of the ionized bubbles and also their percolation behaviour differs substantially. Even
though the neutral islands are relatively rare, they will be easier to identify in observations with the low frequency component of the Square Kilometre Array due to their larger size and the lower noise levels at lower redshifts. The size distribution of neutral islands at the late stages of reionization is found to depend on the source properties, such as the ionizing efficiency of the sources and their minimum mass.We find the longest line of sight through a neutral region to be more than 100 comoving Mpc until very late stages (90–95 per cent reionized), which
may have relevance for the long absorption trough at z = 5.6–5.8 in the spectrum of quasar ULAS J0148+0600.

Item Type: Article
Keywords: methods: statistical – techniques: image processing – techniques: interferometric – dark ages, reionization, first stars – early Universe – radio lines: galaxies
Schools and Departments: School of Mathematical and Physical Sciences > Physics and Astronomy
Subjects: Q Science > QC Physics
Depositing User: Amelia Redman
Date Deposited: 24 Oct 2019 07:35
Last Modified: 24 Oct 2019 09:01
URI: http://sro.sussex.ac.uk/id/eprint/87240

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