Abstract We study star formation over ∼12 Gyr using pop-cosmos, a generative model trained on 26-band photometry of ∼420,000 COSMOS2020 galaxies (Spitzer IRAC Ch. 1 26). The model learns distributions over 16 stellar population synthesis parameters via score-based diffusion, matching observed colours and magnitudes. We use pop-cosmos to compute the cosmic star formation rate density (SFRD) to z = 3.5 by directly integrating individual galaxy SFRs. The SFRD peaks at z = 1.3 ± 0.1, Δz ≃ 0.6 later than previous canonical estimates, with peak value 0.08 ± 0.01 M⊙ yr−1 Mpc−3. We classify star-forming (SF) and quiescent (Q) galaxies using specific SFR 10−11 yr−1, comparing with NUVrJ colour selection. The sSFR criterion yields up to 20 per cent smaller quiescent fractions across 0 z 3.5, with NUVrJ-selected samples contaminated by galaxies with sSFR up to 10−9 yr−1. Our sSFR-selected stellar mass function shows a negligible number density of low-mass (≲ 109.5 M⊙) Q galaxies at z ≃ 1, where colour-selection shows a prominent increase. Non-parametric star formation histories around the SFRD peak reveal distinct patterns: SF galaxies show gradually weakening correlations between their recent and earlier SFRs, implying increasingly stochastic star formation toward early epochs. Q galaxies exhibit full correlation (r 0.95) during the most recent ∼300 Myr, then sharp decorrelation with earlier star-forming epochs, marking clear quenching transitions. Massive (10 log10(M*/M⊙) 11) galaxies quench on a time-scale of ∼1 Gyr, with mass assembly concentrated in their first 3.5 Gyr. Finally, AGN activity (infrared torus luminosity fraction) peaks as massive (∼1010.5 M⊙) galaxies approach the transition between star-forming and quiescent states, declining sharply once quiescence is established. This provides evidence that AGN feedback operates in a critical regime during the ∼1 Gyr quenching transition.
Deger et al. (Tue,) studied this question.