Observations with the James Webb Space Telescope have revealed a high abundance of bright z>10 galaxy candidates that challenge the predictions of standard theoretical models, particularly at the highest redshifts. Various explanations for this discrepancy have been proposed, such as feedback-free starbursts, radiation-driven outflows clearing the dust from star-forming regions, a top-heavy...
The discovery of an unexpectedly high N/O ratio in GN-z11 raises questions about star formation in the early universe. Using public NIRSpec data, we have pinpointed additional two galaxies at z=6.23-8.68 with nitrogen-rich gas relative to carbon and oxygen ([N/C] $\gtrsim$ 1 and [N/O] $\gtrsim$ 0.5), suggestive of predominant materials processed by the CNO cycle. Interestingly, using the...
The observations conducted with JWST have disclosed galaxies at high redshifts characterized by extremely high N/O and low C/N ratios, exemplified by GN-z11. The high N/O and low C/N ratios of these galaxies are largely biased toward the equilibrium of the CNO cycle, suggesting that these three galaxies are enriched by metals processed by the CNO cycle. The low C/N and high N/O ratios of these...
We explore the nature of the first galaxies using a semi-analytic model tailored for the rapidly evolving early Universe (Ventura et al. 2024). Applying this model to an N-body simulation enables us to resolve molecularly cooled minihalos down to ~1e5Msol within a cosmological volume of 10/h cMpc. By tracking chemical enrichment both inside and outside these first galaxies, we follow closely...
By performing 3D radiation hydrodynamics simulations with radiative and stellar wind feedback, we study the formation of young massive star clusters (YMCs). We include the metal yield from stellar wind and supernovae. We find that the young massive star clusters are only born in the high-surface density clouds where radiative feedback becomes ineffective due to strong gravitational force from...
How do the morphologies of the most distant high-z galaxies evolve from cosmic dawn to the present-day? How do they build up mass and structure and what can this tell us about bulge growth, structure formation, and Early-type galaxy formation? These questions are of vital importance to both observations and simulations and are crucial in understanding the physical properties of high-z...
JWST has opened a new chapter in our understanding of early star formation, unveiling a surprising number of luminous galaxies at z>10, as well as the first quenched low-mass galaxies. This coexistence of extreme sources, exhibiting a wide range of star formation rates, suggests a highly stochastic evolution and raises fundamental questions. Are galaxies more bursty at high-z and why? How does...
Feedback from supernovae and radiation emitted by stars plays a pivotal role in shaping the early universe. These feedback processes have a direct influence on gas and stellar dynamics, leaving discernible traces in observational data. I introduce SPICE, a novel suite of radiation-hydrodynamical simulations targeting cosmic reionization. SPICE uses RAMSES-RT to track the propagation of...
