A Comparison of Star-formation Histories Derived from UniverseMachine and LEGA-C at 0.6 < z < 1

Abstract In this work, we compare star formation histories of massive (10.5 < log ( M * / M ⊙ ) < 12) galaxies in the UniverseMachine model to those measured from the Large Early Galaxy Astrophysics Census (LEGA-C) at 0.6 < z < 1. Following the LEGA-C study, we investigate how 50% (t 50) and 90% (t 90) formation timescales depend on total stellar mass. We find good agreement between the observed and model timescales for the star-forming population Δ t SF ≲ 1 Gyr across the full mass range. In contrast, the observed age-mass correlation is weaker for the quiescent population compared to UniverseMachine models (Δt Q ≲ 2 Gyr), especially at the high-mass end. This indicates continued star formation or additional processes in the most massive quiescent galaxies, a behavior not accounted for in the UniverseMachine model.