Time:　1:20pm~3:10pm, October 16 (Thursday)

Title:　Three years of searching for the most distant galaxies with JWST and what have we learned so far?

Speaker: Dr. Aaron Yung, Giacconi Fellow

Affiliation: Space Telescope Science Institute (STScI)

Place: Science Building III SC157

Abstract:
The superb capabilities of the James Webb Space Telescope (JWST) have extended our view to the ultra-high-redshift universe (z > 12). Among numerous scientific discoveries enabled by JWST, some early deep extragalactic observations have unexpectedly revealed an abundance of massive galaxies, presenting significant challenges to conventional galaxy formation models. To address this cosmic puzzle, we utilize some well-established galaxy formation models in conjunction with state-of-the-art cosmological simulations to seek understanding of physical mechanisms that enabled extremely rapid star formation activities in the early universe. We investigated and quantified the impact of various sources of uncertainty, including a potentially evolving mass-to-light ratio driven by changes in the IMF, underestimated field-to-field variance, and significant uncertainties in photometric redshifts, among others. Our study also examines the number density of halo populations during this epoch, alongside the gas cooling rates and star formation efficiencies of galaxies. I will also present new simulated results for various alternative star formation and stellar feedback models and discuss the essential conditions required to reproduce the observed ultra-high-redshift galaxy populations.

Title: Bitter-sweet symphonies of planet formation

Speaker: Dr. Min-Kai Lin, Associate Research Fellow
(Institute of Astronomy and Astrophysics, Academia Sinica)

Place: Science Building III SC162

Abstract: The study of quantum systems coupled to an environment plays a vital role in how we measure temperatures of the coldest and hottest matter in the universe. The strategy relies on introducing impurities into the system of interest and on observing how these probe particles evolve towards or in equilibrium with their surroundings, from which we may in turn deduce the thermal properties of that environment. Originally studied in the context of condensed matter physics, open quantum systems nowadays provide a common language to research spanning multiple orders of magnitude in temperature, ranging from Bose Einstein condensates made of ultracold atoms to the Quark-Gluon plasma created in ultra-relativistic collisions of heavy ions. This talk builds a bridge from polaron impurities in the former to quarkonium particles in the latter as two manifestations of quantum Brownian motion, a phenomenon ideally described by open quantum systems.