Colloquium on Oct. 8, 2026

From Metal-Poor Gas to a Dusty Universe

Speaker: Siwei Zou (CAS)

Venue: SWIFAR Building 2111

Time: 16:00 PM, Thursday, Oct. 8, 2026

Abstract:

How did a nearly pristine Universe become populated by dusty galaxies, and where can we still find the chemical traces of its earliest stars? I will explore these questions through two complementary views of galaxy evolution: the gas that records past enrichment and the galaxies undergoing rapid growth. Using distant quasars as background sources, absorption spectroscopy reveals gas too faint to image directly, allowing us to measure its composition and search for signatures of the first stellar generations. I will discuss how unusual abundance patterns and exceptionally cold gas embedded in an ionized medium offer insights into the chemical history and physical structure of gas surrounding galaxies. I will then turn to the dusty Universe revealed by JWST and ALMA. Recent COSMOS-3D observations show that dusty galaxies inhabit remarkably diverse environments when the Universe was roughly a billion years old. Interacting systems exhibit the strongest concentrations of nearby companions, while galaxies with hot-dust signatures and possible obscured nuclear activity show no comparable enhancement. These differences offer clues to how interactions, star formation, and black hole growth unfold within assembling cosmic structures. Connecting these perspectives, I will examine how gas and environment shape the build-up of heavy elements, and where the chemical legacy of the earliest stars may survive subsequent galaxy growth.

Report PPT： SWIFAR_Siwei Zou.pdf