The 21 cm Signature of Cosmic String Wakes

Abstract

We discuss the signature of a cosmic string wake in 21cm redshift surveys. Since 21cm surveys probe higher redshifts than optical large-scale structure surveys, the signatures of cosmic strings are more manifest in 21cm maps than they are in optical galaxy surveys. We find that, provided the tension of the cosmic string exceeds a critical value (which depends on both the redshift when the string wake is created and the redshift of observation), a cosmic string wake will generate an emission signal with a brightness temperature which approaches a limiting value which at a redshift of $z+1=30$ is close to 400 mK in the limit of large string tension. The signal will have a specific signature in position space: the excess 21cm radiation will be confined to a wedge-shaped region whose tip corresponds to the position of the string, whose planar dimensions are set by the planar dimensions of the string wake, and whose thickness (in redshift direction) depends on the string tension. For wakes created at $z_i+1=10^3$, then at a redshift of $z+1=30$ the critical value of the string tension $\mu$ is $G\mu =6\times 10^{-7}$, and it decreases linearly with redshift (for wakes created at the time of equal matter and radiation, the critical value is a factor of two lower at the same redshift). For smaller tensions, cosmic strings lead to an observable absorption signal with the same wedge geometry.

11 pages, 4 figures; a couple of comments added in the discussion section

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Cited by in corpus (4)

• Background reionization history from omniscopes
• Cosmic Strings as Emitters of Extremely High Energy Neutrinos
• Constraints on Superconducting Cosmic Strings from Early Reionization
• Level Crossing Analysis of Cosmic Microwave Background Radiation: A method for detecting cosmic strings