21-cm Lensing and the Cold Spot in the Cosmic Microwave Background

An extremely large void and a cosmic texture are two possible explanations for the cold spot seen in the cosmic microwave background. We investigate how well these two hypotheses can be tested with weak lensing of 21-cm fluctuations from the epoch of reionization measured with the Square Kilometer Array. While the void explanation for the cold spot can be tested with Square Kilometer Array, given enough observation time, the texture scenario requires significantly prolonged observations, at the highest frequencies that correspond to the epoch of reionization, over the field of view containing the cold spot.

Figure 1

The signal-to-noise with which SKA can detect a void matching the WMAP cold spot as a function of observation time over the field of view containing the cold spot, calculated numerically. In black we plot the prospects for the current plan of SKA and in dashed gray those for SKA with four times the coverage fraction $f_{\mathrm{cover}}$.