Speaker
Description
Galaxy clusters offer an unconventional route to the global 21 cm signal. The low-frequency background passing through the hot intracluster medium is inverse Compton-scattered, producing a cluster-localised spectral distortion, the SZE-21cm, that carries the imprint of the global signal. Since it is measured as a difference between a cluster sightline and nearby blank sky, the effect does not depend on absolute calibration of the sky monopole and is well suited to interferometric observation. This work makes the case for the SZE-21cm as a Cosmic Dawn probe. Simulated differential observations with realistic instrumental effects show that the spectrum can potentially be recovered with SKA1-Low and used to independently test anomalous global-signal claims such as EDGES. A variance-aware analysis across physically motivated Cosmic Dawn scenarios further shows that heating histories leave separable imprints in the SZE-21cm once intrinsic 21 cm sky fluctuations are accounted for, with robust discrimination requiring stacking over large cluster samples. The SZE-21cm offers an independent consistency test on early-Universe heating histories, complementary to global-signal and power-spectrum approaches, and worth keeping in view as SKA-Low moves towards Science Verification.