2024-01-11 Abstract
Title: JWST is observing the first star clusters: one giant leap towards observing the first stars
Speaker: Mr. Yu-Yang (Tiger) Hsiao (John Hopkins)
Date: January 11 at 14:30
Location: R521, General Building II
Abstract:
The eagerly awaited discovery of the first generation of stars and galaxies raises several key scientific questions: Are they strong enough to ionize the intergalactic medium? Do they truly lack metals? However, directly detecting individual first generation of stars remains a formidable challenge, even in the era of the JWST, which requires serendipitous discovery in gravitationally lensed fields. Instead, the combined light from a cluster of stars may reach the required brightness to be detected. Within the first year of observation, JWST has taken a giant leap towards unraveling the mystery of the first star clusters. For instance, star clusters with radii down to several pc have been observed in high-redshift galaxies such as SMACS0723, the Sparkler, Sunrise Arc, MACS0647-JD, GN-z11, and the Cosmic Gem’s Arc. In our JWST Cycle 1 & 2 programs, we observed several galaxy clusters, which strongly magnified distant objects. MACS0647-JD, a galaxy at z=10.17, was resolved as having two components, possibly star clusters within a single galaxy with radii of few tens of pc. We derived a metalicity of ~6 - 20% Zsun from the emission lines with NIRSpec. In Cosmic Gem’s Arc (z~10), we spotted blue star clusters (beta < -2) with radii of ~1 pc, possibly having no or very little metals. Future JWST observations will help us understand and discover even more first star clusters.