http://arxiv.org/abs/1401.5563
Warm dark matter (WDM) with mass m_WDM=O(1) keV has long been discussed as a promising solution for discrepancies between cosmic structures observed at small scales and predications of the concordance CDM model. Though several cosmological observations such as the Lyman-alpha forest have already begun to constrain the range of m_WDM, WDM is yet to be fully excluded as a solution for these so-called small-scale problems. In this paper, we study 21 cm line fluctuations from minihalos in a WDM model and evaluate constraints on m_WDM for future cosmological 21 cm surveys, such as SKA and FFTT. We show that, since WDM with mass m_WDM>10 keV decreases the abundance of minihalos by suppressing the matter power spectrum on small scales via free-streaming, such WDM can significantly affect the resultant 21 cm line fluctuations from minihalos. We find SKA and FFTT can give a lower bound m_WDM>20 keV and 30 keV, respectively, which are tighter than the current constraint. These future 21 cm surveys might be able to rule out a WDM model as a solution of small-scale problems.
Thu, 23 Jan 14
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