"Quest for the Most Distant Universe – Today and Beyond"

Uncovering and characterizing the earliest systems in the universe is essential for addressing fundamental cosmological questions — including the emergence of the first galaxies and black holes (BHs), and the timeline of cosmic reionization. The advent of JWST has revolutionized our ability to detect and study galaxies from these early epochs, now extending the frontier of confirmed systems to z ~ 20. At the same time, submm/mm observations with ALMA are providing complementary insights into the cold dust and gas components that trace early star formation. In this talk, I will present my recent efforts to explore the most distant universe through a synergistic approach combining JWST, ALMA, and gravitational lensing, enabling the most sensitive and comprehensive investigations of the earliest phases of galaxy formation. My systematic JWST spectroscopic survey confirms the high abundance of z > 9 galaxies previously suggested by photometric studies, and I will discuss possible origins of this surprising excess based on our initial characterizations. I will also introduce the first infrared luminosity function derived from the largest faint ALMA sample ever compiled, allowing a direct estimate of the total (unobscured + dust-obscured) cosmic star formation history up to z ~ 8. Our joint JWST and ALMA deep follow-up observations of a strongly lensed early galaxy reveal that what appears as a single disk-like structure is resolved into at least 15 individual young massive star clusters with effective radii of 10–50 pc, dominating ~70% of the galaxy’s total flux and embedded within a smooth rotating disk (V/σ ~ 3). These findings suggest that stellar feedback is remarkably weak at these epochs, providing a plausible explanation for the enhanced star formation activity inferred from our rest-UV and FIR studies. At the end of my talk, I will also introduce my ~300-hour Cycle 4+5 JWST treasury program, Vast Exploration for Nascent, Unexplored Sources (VENUS) — JWST’s first wide lensing-cluster survey. Designed to fully harness the power of gravitational lensing, VENUS aims to uncover the faintest and earliest galaxies across cosmic time, and I will present some of its initial outcomes showcasing the transformative potential of this new endeavor.