The 21-cm signals from ultracompact minihaloes as a probe of primordial small-scale fluctuations
The 21-cm signals from ultracompact minihaloes as a probe of primordial small-scale fluctuations
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DOI：
10.1093/mnras/staa1033
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发表时间：
2020-02
影响因子：
4.8
通讯作者：
Kunihiko Furugori;K. Abe;Toshiyuki Tanaka;Daiki Hashimoto;H. Tashiro;K. Hasegawa
中科院分区：
文献类型：
--
作者：
Kunihiko Furugori;K. Abe;Toshiyuki Tanaka;Daiki Hashimoto;H. Tashiro;K. Hasegawa
如果暗物质的密度波动在小尺度上具有显著的大振幅，则可以在物质-辐射相等时代之后形成超紧凑微晕。对UCMH丰度的限制使我们能够获得这种小规模的波动。在本文中，我们提出，通过测量再电离时代之前的21厘米波动，我们可以获得对UCMH丰度的约束。我们计算了来自UCMHs的21厘米信号，并表明UCMHs提供了21厘米波动的增强。我们还研究了UCMH丰度和小尺度曲率扰动的约束。我们的研究结果表明，即将进行的21厘米观测，即平方公里阵列（SKA），提供了对原始曲率功率谱振幅的约束，${\cal A}_{\zeta} \lesssim 10^{-6}$在$100~{\rm Mpc}^{-1} \lesssim k \lesssim 1000~{\rm Mpc}^{-1}$。尽管它并不比UCMHs中暗物质湮灭引起的伽马射线未探测到的约束强，但SKA的约束将是重要的，因为这种约束是独立于暗物质粒子模型的。
Ultracompact minihalos~(UCMHs) can form after the epoch of matter-radiation equality, if the density fluctuations of dark matter have significantly large amplitude on small scales. The constraint on the UCMH abundance allows us to access such small-scale fluctuations. In this paper, we present that, through the measurement of 21-cm fluctuations before the epoch of reionization~ we can obtain a constraint on the UCMH abundance. We calculate the 21-cm signal from UCMHs and show that UCMHs provide the enhancement of the 21-cm fluctuations. We also investigate the constraint on the UCMH abundance and small-scale curvature perturbations. Our results indicate that the upcoming 21-cm observation, the Square Kilometre Array (SKA), provides the constraint on amplitude of primordial curvature power spectrum, ${\cal A}_{\zeta} \lesssim 10^{-6}$ on $100~{\rm Mpc}^{-1} \lesssim k \lesssim 1000~{\rm Mpc}^{-1}$. Although it is not stronger than the one from the non-detection of gamma rays induced by dark matter annihilation in UCMHs, the constraint by the SKA will be important because this constraint is independent of the dark matter particle model.