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arXiv · 2112.10464

Anisotropies in Cosmological 21 cm Background by Oscillons/I-balls of Ultra-light Axion-like Particle

Masahiro Kawasaki·Kazuyoshi Miyazaki·Kai Murai·Hiromasa Nakatsuka·Eisuke Sonomoto
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Abstract

Ultra-light axion-like particle (ULAP) with mass $m \sim 10^{-22} ~\mathrm{eV}$ has recently been attracting attention as a possible solution to the small-scale crisis. ULAP forms quasi-stable objects called oscillons/I-balls, which can survive up to a redshift $z \sim 10$ and affect the structure formation on a scale $\sim \mathcal{O}(0.1)~\mathrm{Mpc}$ by amplifying the density fluctuations. We study the effect of oscillons on 21~cm anisotropies caused by neutral hydrogen in minihalos. It is found that this effect can be observed in a wide mass range by future observations such as Square Kilometer Array~(SKA) if the fraction of ULAP to the total dark matter density is $\mathcal{O}(0.01 \text{--} 0.1)$.

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Masahiro Kawasaki, Kazuyoshi Miyazaki, Kai Murai, Hiromasa Nakatsuka, Eisuke Sonomoto. 2021-12-20. Anisotropies in Cosmological 21 cm Background by Oscillons/I-balls of Ultra-light Axion-like Particle. https://doi.org/10.1088/1475-7516%2F2022%2F08%2F066

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