Title: The COLIBRE project: introducing a suite of new cosmological simulations of galaxy formation that include a cold gas phase
Speaker: Evgenii Chaikin (Leiden University)

Abstract:
In this talk, I will provide an overview of the new cosmological hydrodynamical simulations of galaxy formation, COLIBRE. The simulations are available at three resolution levels, with gas particle masses of Mgas = 1.5e7, 1.8e6, and 2.3e5 Msun, in cosmological volumes of up to 400^3, 200^3, and 50^3 comoving Mpc^3, respectively. COLIBRE improves upon the previous generation of galaxy formation simulations by self-consistently including a cold gas phase, non-equilibrium cooling of primordial elements, and a prescription for the formation and evolution of dust grains coupled to the chemistry solver. In addition to describing the critical aspects of the galaxy formation physics implemented in COLIBRE, I will explain the calibration procedure of the simulations, where the strengths of energy feedback from supernovae and active galactic nuclei were optimised using machine learning to reproduce the z = 0 observed galaxy stellar mass function and size–stellar mass relation. Finally, I will present the first results of the COLIBRE simulations on galaxy stellar masses, sizes, atomic and molecular hydrogen content, the metal enrichment, and the growth of supermassive black holes.

Bio:
Evgenii received his Bachelor's degree in Astrophysics with honours in 2017 from the Peter the Great Saint-Petersburg Polytechnic University in Russia. He then moved to Germany and earned a Master's degree from the University of Bonn. In 2019, Evgenii moved to Leiden University as a PhD candidate to join an international team developing the new state-of-the-art simulations of galaxy formation, COLIBRE. He defended his PhD thesis with honours in 2024 and began a post-doctoral position at the same university to help complete the development of the simulations. The final stages of the COLIBRE development and the largest COLIBRE simulations were completed in the second half of 2025, thereby fulfilling the primary objective of Evgenii's work at Leiden University over the past six years.