Where giants dwell: Probing the environments of early massive quiescent galaxies

We investigated the environments of massive quiescent galaxies at 3 ≲ z ≲ 5 using the GAlaxy Evolution and Assembly (GAEA) theoretical model. We selected galaxies with stellar mass above 10 10.8 M ⊙ and specific star formation rates below 0.3 × t −1 +460 Hubble , thus yielding a sample of about 5000 galaxies within a simulated volume of ∼685 Mpc. These galaxies have formation times that cover the range inferred from recent observational data well, including a few rare objects with very short formation timescales and early formation epochs. Model high- z quiescent galaxies are α -enhanced and exhibit a wide range of stellar metallicity, which is in broad agreement with current observational estimates. Massive high- z quiescent galaxies in our model occupy a wide range of environments, from void-like regions to dense knots at the intersections of filaments. Quiescent galaxies in under-dense regions typically reside in halos that collapsed early and grew rapidly at high redshift, though this trend becomes difficult to identify observationally due to large intrinsic scatter in star formation histories. The descendants of high- z massive quiescent galaxies display a broad distribution in mass and environment by z = 0, reflecting the stochastic nature of mergers. About one-third of these systems remain permanently quenched, while most rejuvenation events are merger-driven and more common in overdense regions. Our results highlight the diversity of early quiescent galaxies and caution against assuming that all such systems trace the progenitors of present day most massive clusters.