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

TL;DR

This paper explores how future 21-cm weak lensing observations with SKA can differentiate between the void and texture hypotheses for the cosmic microwave background cold spot, highlighting observational requirements for each scenario.

Contribution

It assesses the feasibility of testing the void and texture explanations for the cold spot using SKA's 21-cm lensing measurements during the epoch of reionization.

Findings

Void hypothesis can be tested with SKA within reasonable observation time.

Texture hypothesis requires significantly longer observations at high frequencies.

Different observational strategies are needed for each scenario.

Abstract

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 (EoR) measured with the Square Kilometer Array (SKA). While the void explanation for the cold spot can be tested with SKA, given enough observation time, the texture scenario requires significantly prolonged observations, at the highest frequencies that correspond to the EoR, over the field of view containing the cold spot.