Abstract
Galactic disks experienced a critical phase of rapid evolution 8–10 billion years ago (Cosmic Noon; redshift = 1–3), shaping the morphological types seen in the local Universe. Thanks to JWST, we can now resolve the characteristic substructures like galactic bulges, bars, spiral arms, and star-forming clumps. Studying their properties provides a glimpse into the evolutionary state of the host disks. I will present results from a series of works where we have successfully modelled the various substructures and thereby revealed their properties. We find that the large fraction of bars in Cosmic Noon star-forming galaxies feature flat profiles, usually seen in mature quiescent systems in the local Universe. Meanwhile, the abundant massive (0.1 pc–1 kpc) star-forming clumps in these systems are found to have a hierarchical nature similar to star-forming regions of local galaxies, suggesting fundamental similarities. These clumps may also be sheared by the differential rotation of the disk, giving rise to spiral arms. However, some of the spiral arms feature clear density-wave-like characteristics, suggesting the presence of sustained quasi-static global oscillations in disks by z ~ 1. Finally, I will share results suggesting that the spiral arms and bars drive centralised star-formation, indicated by the compact dust-emission distribution seen in ALMA sub-mm imaging. Hence, our results provide observational evidence for secular evolution of disks into compact systems at Cosmic Noon, and reveal the role of disk-substructures.
