We study the statistical properties of the cosmological 21 cm signal from both the intergalactic medium ( IGM ) and minihalos , using a reionization simulation that includes a self–consistent treatment of minihalo photoevaporation .
We consider two models for minihalo formation and three typical thermal states of the IGM – heating purely by ionization , heating from both ionizing and Ly \alpha photons , and a maximal ” strong heating ” model .
We find that the signal from the IGM is almost always dominant over that from minihalos .
In our calculation , the differential brightness temperature , { \delta } T _ { b } , of minihalos is never larger than 2 mK .
Although there are indeed some differences in the signals from the minihalos and from the IGM , even with the planned generation of radio telescopes it will be unfeasible to detect them .
However , minihalos significantly affect the ionization state of the IGM and the corresponding 21 cm flux .