Effects of chemically homogeneous evolution of the first stars on the 21-cm signal and reionization
The first generation of stars, known as Population III (Pop III), played a crucial role in the early Universe through their unique formation environment and metal-free composition. These stars can undergo chemically homogeneous evolution (CHE) due to fast rotation, becoming more compact and hotter/b...
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| Main Authors: | , , , , , , , , |
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| Format: | Article (Journal) |
| Language: | English |
| Published: |
August 2025
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| In: |
Monthly notices of the Royal Astronomical Society
Year: 2025, Volume: 541, Issue: 4, Pages: 3113-3133 |
| ISSN: | 1365-2966 |
| DOI: | 10.1093/mnras/staf1178 |
| Online Access: | Verlag, kostenfrei, Volltext: https://doi.org/10.1093/mnras/staf1178 Verlag, kostenfrei, Volltext: https://academic.oup.com/mnras/article/541/4/3113/8210401 
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| Author Notes: | Boyuan Liu, Daniel Kessler, Thomas Gessey-Jones, Jiten Dhandha, Anastasia Fialkov, Yves Sibony, Georges Meynet, Volker Bromm and Rennan Barkana |
| Summary: | The first generation of stars, known as Population III (Pop III), played a crucial role in the early Universe through their unique formation environment and metal-free composition. These stars can undergo chemically homogeneous evolution (CHE) due to fast rotation, becoming more compact and hotter/bluer than their (commonly assumed) non-rotating counterparts. In this study, we investigate the impact of Pop III CHE on the 21-cm signal and cosmic reionization under various assumptions on Pop III star formation, such as their formation efficiency, initial mass function, and transition to metal-enriched star formation. We combine stellar spectra computed by detailed atmosphere models with seminumerical simulations of Cosmic Dawn and the epoch of reionization ($z\sim 6-30$). The key effect of CHE arises from the boosted ionizing power of Pop III stars, which reduces the Pop III stellar mass density required to reproduce the observed Thomson scattering optical depth by a factor of $\sim 2$. Meanwhile, the maximum 21-cm global absorption signal is shallower by up to $\sim 15$ mK (11 per cent), partly due to the reduced Lyman-band emission from CHE, and the large-scale ($k\sim 0.2\ \rm cMpc^{-1}$) power drops by a factor of a few at $z\gtrsim 25$. In general, the effects of CHE can be comparable to those of Pop III star formation parameters, showing an interesting interplay with distinct features in different epochs. These results highlight the importance of metal-free/poor stellar evolution in understanding the early Universe and suggest that future studies should consider joint constraints on the physics of star/galaxy formation and stellar evolution. |
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| Item Description: | Online verfügbar: 22. Juli 2025, Artikelversion: 29. Juli 2025 Gesehen am 09.12.2025 |
| Physical Description: | Online Resource |
| ISSN: | 1365-2966 |
| DOI: | 10.1093/mnras/staf1178 |