Surrounding every galaxy is a vast gas halo, crucial for its development. This circumgalactic medium, difficult to observe directly, plays a key role in supplying fresh gas and managing expelled matter. Current models, often based on equilibrium assumptions, struggle to capture its full complexity. To address this gap, the MEGATRON project was initiated, now revealing the decisive influence of non-equilibrium physics and local stellar radiation on our understanding of this environment.
The unprecedentedly precise cosmological simulations developed by the MEGATRON team explore four major scientific challenges. They highlight the emission of hydrogen-beta and oxygen induced by radiation, the early formation of molecules like H2 and CO in distant galaxies, how different ions trace distinct gas phases within the circumgalactic medium, and the link between dark matter and the formation of cosmic structures.
Five articles from MEGATRON address complementary aspects: the first stars, chemical enrichment, spectra of distant galaxies observable with the James Webb Space Telescope (JWST), the interstellar medium, and the surrounding gas. The common goal is to understand the young Universe by simultaneously tracking light, chemistry, stars, and matter exchange within a unified physical framework.
These discoveries are transforming our view of the gaseous halo, revealing that the gas retains a 'memory' of its history and its properties do not adjust instantaneously. These advancements, significantly altering observables, promise a more refined interpretation of JWST data and open new avenues for studying the matter cycle, from the formation of the first stars to galactic maturity.
