Sirichai Chongchitnan, Joseph Silk
We present a new probe of primordial non-Gaussianity via the 21cm radiation from minihalos at high redshifts. We calculate the fluctuations in the brightness temperature (measured against the cosmic microwave background) of the 21cm background from minihalos containing HI, and find a significant enhancement due to small non-Gaussianity with amplitude f_NL=O(1). This enhancement can be attributed to the nonlinear bias which is increased in the presence of non-Gaussianity. We show that our results are robust against changes in the assumed mass function and some physical aspects of minihalo formation, but are nevertheless sensitive to the presence of strong radiation sources within or around the minihalos. Our results are relevant for constraining and searching for small primordial non-Gaussianity with upcoming radio telescopes such as LOFAR and SKA.
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http://arxiv.org/abs/1205.6799
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