Title: EDGES Disfavors Excess Radio Background and Interacting Dark Matter

Speaker: Dr. Junsong Cang (Scuola Normale Superiore and SlSSA)

Time: 10:00am, August 20, 2025

Location: 3-402, PMO Xianlin Campus

Abstract: The first global 21cm signal reported by EDGES featured an absorption trough centered around redshift 17 with a depth of -500 mK, such deep signal can be achieved by either an excess radio background or cooling induced by interactions between dark matter and baryon. We re-analysed the EDGES sky temperature data with physically motivated cosmic 21cm signal models driven by either interacting dark matter or excess radio background from Pop III galaxies, we jointly forward modelled the foreground contamination and experimental calibration residuals. Opposite to the initial EDGES claim, our result shows that for excess radio background model, the posteriors for 21cm brightness temperature obtained with EDGES data remain entirely consistent with the standard model. Our preliminary analysis with interacting dark matter also points to similar results. Future experiments like Hongmeng can further constrain global 21cm signal evolution and potentially give extremely stringent constraints on interacting dark matter and early radio galaxies.