ASTRONOMY COLLOQUIUM

Over the decades, astronomers have discussed how stars form in the first galaxies at very high redshifts. For examples, massive stars may be selectively produced due to missing coolants of metals, which may create seed black holes for supermassive black holes via a direct collapse, and globular clusters might form through a physical mechanism that is very different from present-day star formation. I will present recent progress in observational studies of early galaxy formation at z~10 uncovered using various JWST photometric and spectroscopic data, and discuss luminosity functions and cosmic star-formation history suggestive of very efficient star-formation. I will also discuss the possibility that elemental abundance ratios, beyond oxygen, in early galaxies are related to globular cluster formation and possibly direct collapse. A moderately high fraction of these early galaxies harbor faint AGN, which contribute to cosmic reionization more than previously expected before the launch of JWST, consistent with the late cosmic reionization history. Finally, I will introduce ongoing efforts to explore the important epoch of cosmic reionization through the combination of 21cm observations and Subaru large-area massive spectroscopy for high-redshift galaxies.

To view this talk via YouTube, please visit: https://www.youtube.com/playlist?list=PLb1880Rn0qkKFkWyROUq1kRlgCsuBTrnd