Tracing the Assembly of the First Massive Galaxies with a Digital Twin
Mahsa Kohandel (Scuola Normale Superiore, Pisa)
Tuesday 30/09/2025 @ 14:00, Sala Antonio Sollima (IV piano Battiferro)
The discovery of luminous galaxies at z>10 by JWST and ALMA has opened a new frontier in our understanding of galaxy formation, revealing systems that appear massive, metal-enriched, and surprisingly mature only a few hundred million years after the Big Bang. To interpret these findings, I will introduce Amaryllis, a high-resolution zoom-in simulation from the SERRA suite that acts as a “digital twin” of these early galaxies. Amaryllis allows us to follow the growth of a representative system from its first appearance at z~16 to z~7, connecting the population of bright, compact galaxies at cosmic dawn to the massive galaxies observed by the end of Reionization. I will show how extreme [O III]/[C II] line ratios, broad [O III] wings, and bursty star formation arise transiently during merger-driven episodes, while at the same time a dynamically cold gaseous disk emerges by z?11. This coexistence of ordered rotation with violent bursts and outflows occurs within a massive but otherwise typical ?CDM halo, showing that such systems do not require exotic physics. I will conclude by highlighting how digital twins like Amaryllis can guide ALMA and JWST strategies to disentangle mergers, feedback, and disk formation in the first massive galaxies at cosmic dawn.