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

Authors :
Kenji Hasegawa
Daiki Hashimoto
Hiroyuki Tashiro
Toshiyuki Tanaka
Katsuya T. Abe
Kunihiko Furugori
Source :
Monthly Notices of the Royal Astronomical Society. 494:4334-4342
Publication Year :
2020
Publisher :
Oxford University Press (OUP), 2020.

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, ${\cal A}_{\zeta} \lesssim 10^{-6}$ 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.<br />Comment: 8pages, 6 figures, published in MNRAS

Details

ISSN :
13652966 and 00358711
Volume :
494
Database :
OpenAIRE
Journal :
Monthly Notices of the Royal Astronomical Society
Accession number :
edsair.doi.dedup.....40a306cb2890db2489d305da6de2f5da