The 21 cm signature of a cosmic string loop

Abstract

Cosmic string loops lead to nonlinear baryon overdensities at early times, even before the time which in the standard LCDM model corresponds to the time of reionization. These overdense structures lead to signals in 21cm redshift surveys at large redshifts. In this paper, we calculate the amplitude and shape of the string loop-induced 21cm brightness temperature. We find that a string loop leads to a roughly elliptical region in redshift space with extra 21cm emission. The excess brightness temperature for strings with a tension close to the current upper bound can be as high as 1 o K for string loops generated at early cosmological times (times comparable to the time of equal matter and radiation) and observed at a redshift of z + 1 = 30. The angular extent of these predicted "bright spots" is about 0.1• for a value of the string tension equal to the current upper bound. These signals should be detectable in upcoming high redshift 21cm surveys.

21 cm angular spectrum of cosmic string loops

“…The Hubble flow also causes the line broadening as considered in Ref. [47]. The redshift difference along the LOS is given as δν = 2Hax t / sin ψ.…”

“…The redshift difference along the LOS is given as δν = 2Hax t / sin ψ. As a result, the intrinsic line profile broadened by the Hubble flow is [47] φ H (ν) = 1/δν |ν − ν * | < δν/2 0 otherwise .…”

“…[47] in which a loop produces the brightness temperature as high as 1 K for Gµ ∼ 10 −7 . This is because they have considered static loops.…”

“…The 21 cm signature due to a static loop have been studied in Ref. [47]. A loop induces a spherical gravitational collapse of matter and produces a bright spot on a redshifted 21 cm map.…”

Constraints on superconducting cosmic strings from early reionization

“…In addition to these signatures that are particular to superconducting strings, there are more generic effects that are gravitational and do not rely on superconductivity. These include the anisotropy of the CMB temperature [17] and B-mode polarization [18,19], gravitational waves [20][21][22][23][24][25], gravitational lensing [26], wakes in the 21-cm maps [27][28][29][30][31], early structure formation [32], early reionization due to early structure formation [33], and formation of dark matter clumps [34].…”