| Abstract: The rich morphological features observed in present-day galaxies emerge as the collective outcome of various physical processes such as rapid dissipative collapse, mergers, dynamical rearrangement, and feedback, which operate over a wide range of timescales. Recent observations with the \textit{James Webb Space Telescope (JWST)}, however, have revealed indications of structural maturity at epochs previously thought to be too early for such complexity. Thus, the epoch at which, and the mechanisms by which, these structures first assembled remain poorly constrained. In this talk, I present results from deep JWST imaging of spectroscopically confirmed galaxies at z>6, demonstrating that distinct bulge and disk components were already beginning to emerge at these early times. We perform detailed morphological modeling of 190 galaxies and identify 20 systems that are well described by a compact inner Sersic component and an underlying exponential disk. These galaxies exhibit high bulge-to-total light ratios (B/T~0.47) and central stellar mass surface densities ($\sim 2.8 \times 10^{8},M_\odot,\mathrm{kpc}^{-2}$), comparable to those of local quiescent galaxies, indicating rapid central mass assembly. We then extend the analysis to spheroidal systems in the sample and discuss their structural properties in the context of present-day galaxy scaling relations. Together, our findings suggest that the assembly of bulges and spheroids is already well underway by z~6, with important implications for the drivers of early structural assembly and the origin of compact quiescent galaxies observed at z~4-5. |
