In De Lucia et al. 2025, we investigate the environments of massive quiescent galaxies at 3 < z < 5 using our GAEA model. We show that model high-z quiescent galaxies are alpha-enhanced and exhibit a wide range of stellar metallicities, in broad agreement with current observational estimates. Massive high-z quiescent galaxies in our model occupy a range of environments, from void-like regions to dense knots at the intersections of filaments. Quiescent galaxies in underdense regions typically reside in halos that collapsed early and grew rapidly at high redshift, though this trend becomes difficult to identify observationally due to a large intrinsic scatter in star formation histories. The descendants of high-z massive quiescent galaxies display a broad distribution in mass and environments at z=0, reflecting the stochastic nature of mergers. About one third of these systems remain permanently quenched in our model, while most rejuvenation events are merger-driven and more common in overdense regions. 

In Cantarella et al 2025, we discuss GAEA predictions for the very high-redshift Universe. We show that GAEA successfully reproduces a wide range of high-z observational estimates including: the galaxy stellar mass function up to z~13 and the galaxies+AGN UV luminosity function up to z~10. We find that UV emission from AGN represents an important contribution at the bright end up to z~8, but becomes negligible at higher redshift. Our model reproduces well the observed mass-metallicity relation at z<4, while it slightly overestimates the normalization of the relation at earlier cosmic epochs. We investigate the impact of different physical mechanisms, such as an enhanced star formation efficiency coupled with a reduced stellar feedback or a negligible stellar feedback at z>10. In the framework of our model, both the galaxy stellar mass and UV luminosity functions at  z>10 can be explained by assuming feedback-free starbursts in high-density molecular clouds. However, we show that this model variant leads to a slight increase of the normalization of the z>10 mass-metallicity relation, strengthening the tension with available data. A model with negligible stellar feedback at  z>10 also predicts larger numbers of massive and bright galaxies aligning well with observations, but it also overestimates the metallicity of the interstellar medium. We show that these model variants can in principle be discriminated using the relation between the star formation rate and galaxy stellar mass.

In Fontanot et al. 2025, we study the properties and environments of z>6 bright quasars as predicted by our GAEA model. We show that at z>6 bright QSOs live in a variety of environments, and that secular processes like disc instability are responsible for triggering roughly the same number of QSOs as galaxy mergers. About half of the regions these high-z QSOs include other active galaxies in sizeable number, the other host galaxies being relatively isolated. The large field-to-field variance in the the number of companions (both active and non-active) recently reported from JWST observations is fairly well reproduced by GAEA predictions. Descendants of host galaxies at z=0 cover a wide range of physical properties and environments with only a small fraction of the hosts of high-z QSOs ending up in massive galaxy clusters. Viceversa, GAEA predicts that only a small fraction of Bright Central Galaxies have a bright z>6 QSOs among their progenitors. Our results suggest that luminous high-z QSO loosely trace the progenitors of low-z galaxy clusters, and that additional information about the environment of high-z QSOs are required to identify the most promising proto-cluster candidates.

Faisst et al. (2025) present the stellar mass-metallicity relation and mass-metallicity star formation relation of 18 massive main sequence galaxies at z~5 from the ALPINE-CRISTAL-JWST sample. Little evolution is found at the massive end of the MZR between z~5 and cosmic noon at a~2, suggesting a fast metal enrichment at early times. Observational estimates are compared to the most recent version (in preparation) of our GAEA model including an explicit treatment for dust. The model is used to interpret current estimates and discuss future evolution of the ALPINE-CRISTAL-JWST galaxies at later cosmic epochs. 

In Xie et al. (2025), we our GAEA model and TNG simulation to investigate whether cluster galaxies suffer from strong RPS that is sufficient to remove a significant fraction of their gas during the first pericentric passage. By tracing the orbit of galaxies since 2.5Rvir, we find in both GAEA and TNG that about half of the galaxies in Virgo-like halos did not suffer strong RPS during the first pericentric passage. In Coma-like halos, almost all galaxies have suffered strong RPS during the first pericentric passage, which can remove all gas from low-mass galaxies but is insufficient to significantly reduce the gas content of more massive galaxies. In general, results from TNG and GAEA are consistent, with the RPS being only slightly stronger in TNG than in GAEA. Our findings suggest that most cluster galaxies maintain a notable fraction of their gas and continue forming stars after the first pericentric passage, except for those with a low stellar mass in very massive halos.