The morphology of the redshifted 21-cm signal from the Cosmic Dawn

Raghunath Ghara, Satadru Bag, Saleem Zaroubi, Suman Majumdar

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The spatial fluctuations in the tomographic maps of the redshifted 21-cm signal from the Cosmic Dawn (CD) crucially depend on the size and distribution of the regions with gas temperatures larger than the radio background temperature. In this article, we study the morphological characteristics of such emission regions and their absorption counterparts using the shape diagnostic tool SURFGEN2 . Using simulated CD brightness temperature cubes of the 21-cm signal, we find that the emission regions percolate at stages with the filling factor of the emission regions FF emi ≳ 0 . 15. Percolation of the absorption regions occurs for FF abs ≳ 0 . 05. The largest emission and absorption regions are topologically complex and highly filamentary for most parts of the CD. The number density of these regions as a function of the volume shows the power-law nature with the power-la w inde x es ≈-2 and -1 . 6 for the emission and absorption re gions, respectiv ely. Ov erall, the planarity , filamentarity , and genus increase with the increase of the volume of both emission and absorption regions.

Original languageEnglish
Pages (from-to)191-202
Number of pages12
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
StatePublished - 1 May 2024

Bibliographical note

Publisher Copyright:
© 2024 The Author(s).


  • cosmology: theory
  • dark ages, reionization, first stars
  • galaxies: formation
  • intergalactic medium
  • radiati ve transfer
  • X-rays: galaxies


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