The Early Universe

The early Universe provides one of the most demanding tests of galaxy-formation models. Galaxies had only a short time to assemble their stellar mass, build structure, and regulate their star formation, making their observed properties especially sensitive to the underlying physical processes.

What I investigate

My research explores galaxy growth and quenching at high and ultra-high redshift, with a particular focus on the first billion years of cosmic history. Key questions include how galaxies assemble stellar mass so rapidly, what regulates their star formation, and how some systems become compact or quiescent at such early times.

A central goal is to test whether physically motivated galaxy-formation models can reproduce the rapidly evolving populations revealed by JWST and other deep surveys, while remaining consistent with galaxy evolution at later epochs.

What we find

Vani et al. 2025 showed that earlier L-Galaxies models reproduce many global galaxy trends out to z ≈10, but exhibit three key shortcomings at high redshift: they underpredict the abundance of massive galaxies, produce too few massive quenched galaxies, and predict quenched systems that are too extended.

Vani et al. 2026 substantially reduces these tensions. The updated model increases the abundance of massive and UV-bright galaxies at z ≥ 9, produces significantly more massive quenched systems at z ≈ 3–8, and forms compact galaxies consistent with observed UV sizes at z ≈ 10–13.

My approach

Within L-Galaxies, I develop and test models in which star formation and stellar feedback depend on the local gas surface density. The framework also includes dissipative mergers and gas- and stellar-disc instabilities, allowing rapid early growth and structural evolution to be followed self-consistently.

Model predictions are compared with high-redshift observations from JWST, including ultraviolet luminosity functions, stellar mass functions, star-formation rates, galaxy sizes, and quenched galaxy abundances.