Title: Probing Cosmic Dawn with 21cm Signals

Speaker: Dr. Yidong Xu (National Astronomical Observatories, CAS)

Time: 14:00pm, August 23, 2023

Location: 3-302, PMO Xianlin Campus

Abstract: Various 21 cm signals from neutral hydrogen have been proposed to probe the cosmic dawn, including the global 21 cm spectrum, the 21 cm tomography, and the 21 cm forest. They will provide valuable insights into the early structure formation during the cosmic dawn. In particular, the 21-cm absorption lines from neutral hydrogen against higher-redshift background sources at cosmic dawn, known collectively as the 21-cm forest, are proposed to simultaneously probe the small-scale structures governed by the dark matter particle mass and the early heating history regulated by the formation of first galaxies. By measuring the 1-D power spectrum of the 21-cm forest, the upcoming Square Kilometre Array (SKA) will be able to shed light on the nature of both the dark matter and the first galaxies. In this talk, I’ll talk about some of the recent progresses on the 21 cm probes for the cosmic dawn, with special focus on the SKA on the ground and the Hongmeng project on lunar orbit.