Probing Helium Reionization Through the $^{3}\mathrm{He}^{+}$ Hyperfine Transition Line
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arXiv
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| Natura: | Preprint |
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2025
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| author | Basu, Arghyadeep Ciardi, Benedetta Garaldi, Enrico |
| author_facet | Basu, Arghyadeep Ciardi, Benedetta Garaldi, Enrico |
| contents | We investigate the hyperfine transition of $^{3}\mathrm{He}^{+}$ as a promising probe of the IGM during the final stages of helium reionization. Utilising the most recent helium reionization simulation, we generate three-dimensional maps of the 3.5cm ($8.67$ GHz) differential brightness temperature and analyze its evolution. Our results show that the volume-averaged brightness temperature declines rapidly from $\sim 1 μ$K at $z = 4$ to $\sim 2.5 \times 10^{-3} μ$K by $z = 2.3$, tracing the HeII to HeIII transition driven by quasars. The power spectrum of the 3.5cm signal exhibits a scale-dependent evolution, peaking on small scales and declining as reionization progresses. We explore the cross-correlation of the 3.5cm transition line with the distribution of AGNs, which shows a transition from positive to negative correlation as ionized regions grow. We also examine the 3.5cm forest and demonstrate that absorption features persist down to $z \sim 2.90$, even when more than $85\%$ of HeII is ionized. Although current observational upper limits lie several orders of magnitude above theoretical predictions, future radio arrays such as $\mathrm{SKA-mid}$ offer promising prospects. Overall, this study highlights the $^{3}\mathrm{He}^{+}$ hyperfine transition as a sensitive tracer of the thermal and ionization history of the IGM during helium reionization. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2510_14059 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Probing Helium Reionization Through the $^{3}\mathrm{He}^{+}$ Hyperfine Transition Line Basu, Arghyadeep Ciardi, Benedetta Garaldi, Enrico Cosmology and Nongalactic Astrophysics Astrophysics of Galaxies We investigate the hyperfine transition of $^{3}\mathrm{He}^{+}$ as a promising probe of the IGM during the final stages of helium reionization. Utilising the most recent helium reionization simulation, we generate three-dimensional maps of the 3.5cm ($8.67$ GHz) differential brightness temperature and analyze its evolution. Our results show that the volume-averaged brightness temperature declines rapidly from $\sim 1 μ$K at $z = 4$ to $\sim 2.5 \times 10^{-3} μ$K by $z = 2.3$, tracing the HeII to HeIII transition driven by quasars. The power spectrum of the 3.5cm signal exhibits a scale-dependent evolution, peaking on small scales and declining as reionization progresses. We explore the cross-correlation of the 3.5cm transition line with the distribution of AGNs, which shows a transition from positive to negative correlation as ionized regions grow. We also examine the 3.5cm forest and demonstrate that absorption features persist down to $z \sim 2.90$, even when more than $85\%$ of HeII is ionized. Although current observational upper limits lie several orders of magnitude above theoretical predictions, future radio arrays such as $\mathrm{SKA-mid}$ offer promising prospects. Overall, this study highlights the $^{3}\mathrm{He}^{+}$ hyperfine transition as a sensitive tracer of the thermal and ionization history of the IGM during helium reionization. |
| title | Probing Helium Reionization Through the $^{3}\mathrm{He}^{+}$ Hyperfine Transition Line |
| topic | Cosmology and Nongalactic Astrophysics Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2510.14059 |