Description
Galaxies experienced a critical phase of rapid evolution 8–10 billion years ago (Cosmic Noon), shaping the morphological types seen in the local Universe, with characteristic features like bulges and spirals. However, direct imaging of these substructures in formation was not possible before JWST. I will present a series of works where we exploit JWST/NIRCam and ALMA images to fully 'deconstruct' Cosmic Noon star-forming galaxies at redshift (z)~1.5 into subcomponents like bulges, disks, star-forming clumps, and spiral arms. The aim is to understand how typical main-sequence galaxies undergo rapid morphological transformations to establish the Hubble sequence. We find that the buildup of the central bulge leads to a lowering of the star-formation efficiency in the host galaxy. However, this is due to the gas being concentrated at the centre, which ends up lowering the efficiency with which gas is converted to stars. Meanwhile, in the disk, we find that star-formation is mainly concentrated in star-forming clumps and spiral arms, both of which are expected to be massive enough to simultaneously funnel gas to the centre. Star-formation in these structures is found to occur over a hierarchy of spatial scales, with mass distributions closely resembling those of star-forming regions in the local Universe. Finally, we study the spiral structures and find a fraction of them exhibiting density-wave-like characteristics. This suggests that the spirals in z>1 galaxies are not just signs of tidal interactions or stochastic star-formation in a differentially rotating disk. In fact, propagating density waves are already in place at z~1.5.
