# High redshift signatures in the 21 cm forest due to cosmic string wakes [CEA]

Cosmic strings induce minihalo formation in the early universe. The resultant minihalos cluster in string wakes and create a “21 cm forest” against the cosmic microwave background (CMB) spectrum. Such a 21 cm forest can contribute to angular fluctuations of redshifted 21 cm signals integrated along the line of sight. We calculate the root-mean-square amplitude of the 21 cm fluctuations due to strings and show that these fluctuations can dominate signals from minihalos due to primordial density fluctuations at high redshift ($z \gtrsim 10$), even if the string tension is below the current upper bound, $G \mu < 1.5 \times 10^{-7}$. Our results also predict that the Square Kilometre Array (SKA) can potentially detect the 21 cm fluctuations due to strings with $G \mu \approx 7.5 \times 10^{-8}$ for the single frequency band case and $4.0 \times 10^{-8}$ for the multi-frequency band case.

Date added: Thu, 17 Oct 13