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

Thursday 30 Oct 2025, 11:00 → 13:00 Asia/Seoul

가동 606호 (백주년기념관)

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.

11:00 → 12:30 Seminar

11:00 Three years of searching for the most distant galaxies with JWST and what have we learned so far?

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.

Speaker: Dr Aaron Yung (NASA STScI)

yung_cv.pdf