The 21-cm signals from ultracompact minihalos as a probe of primordial small-scale fluctuations

Abstract

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, ${\mathcal{A}}_{\zeta }\lesssim 10^{-6}$ on $100{\mathrm{Mpc}}^{-1}\lesssim k\lesssim 1000{\mathrm{Mpc}}^{-1}$. 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.

8pages, 6 figures, published in MNRAS

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Cited by in corpus (11)

• Primordial Black Holes from CDM Isocurvature Perturbations
• Suppressing variance in 21-cm signal simulations during reionization
• Probing the primordial Universe with 21-cm line from cosmic dawn/epoch of reionization
• Constraint on the early-formed dark matter halos using the free-free emission in the Planck foreground analysis
• Dark Freeze-out Cogenesis
• Minihalos as probes of the inflationary spectrum: accurate boost factor calculation and new CMB constraints
• Axionlike Origin of the Primordial Density Perturbation
• Cosmological contribution from population III stars in ultracompact minihalos
• Updated constraints on the primordial power spectrum at sub-Mpc scales
• CMB lensing from early-formed dark matter halos
• Cosmological free-free emission from dark matter halos in the $\Lambda$CDM model