Galaxy assembly and evolution in the P-Millennium simulation: Galaxy clustering

¹ INAF – Astronomical Observatory of Trieste, Via G. B. Tiepolo 11, I-34143 Trieste, Italy
² IFPU – Institute for Fundamental Physics of the Universe, Via Beirut 2, 34151 Trieste, Italy
³ Tianjin Astrophysics Center, Tianjin Normal University, Binshuixidao 393, 300384 Tianjin, China
⁴ EPFL – Institute for Physics, Laboratory for Galaxy Evolution, Observatoire de Sauverny, Chemin Pegasi 51, 1290 Versoix, Switzerland
⁵ ICC – Institute for Computational Cosmology, Department of Physics, Durham University, South Road, Durham DH1 3LE, UK
⁶ Institute for Data Science, Durham University, South Road, Durham DH1 3LE, UK

^⋆ Corresponding author: fabio.fontanot@inaf.it

Received: 28 August 2024
Accepted: 9 May 2025

Abstract

We present the results from the latest version of the GAlaxy Evolution and Assembly (GAEA) theoretical model of galaxy formation coupled with merger trees extracted from the Planck Millennium Simulation (PMS). With respect to the Millennium Simulation, typically adopted in our previous work, the PMS provides a better mass resolution (∼10⁸ h⁻¹ M_⊙), a larger volume (800³ Mpc³), and assumes cosmological parameters consistent with latest results from the Planck mission. The model includes, at the same time, a treatment for the partition of cold gas into atomic and molecular (H₂) components; a better treatment for environmental processes acting on satellite galaxies; an updated modelling of cold gas accretion on supermassive black holes, leading to the phenomenon of active galactic nuclei (AGN) and relative feedback on the host galaxy. We compare GAEA predictions based on the PMS, with model realizations based on other simulations in the Millennium Suite at different resolution, showing that the new model provides a remarkable consistency for most statistical properties of galaxy populations. We interpret this as being due to the interplay between AGN feedback and H₂-based SFR (both acting as regulators of the cold gas content of model galaxies), as model versions considering only one of the two mechanisms do not show the same level of consistency. We then compare model predictions with available data for the galaxy two-point correlation function (2pCF) in the redshift range 0 < z ≲ 3. We show that GAEA runs correctly recover the main dependences of the 2pCF as a function of stellar mass (M_⋆), star formation activity, HI-content, and redshift for M_⋆ > 10⁹ M_⊙ galaxies. These results suggest that our model correctly captures both the distribution of galaxy populations in the large-scale structure and the interplay between the main physical processes regulating their baryonic content, both for central and satellite galaxies. The model predicts a small redshift evolution of the clustering amplitude that results in an overprediction of z ∼ 3 clustering strength with respect to the available estimates, but is still consistent with data within 1σ uncertainties.