Constraining Supermassive Black Hole Seeding and Accretion via Occupation Fractions and Mass-Weighted Distributions

The formation of supermassive black holes (SMBHs) is a key open problem in galaxy evolution, with light- and heavy-seeding models predicting distinct black hole occupation fractions (BHOFs). Using multiwavelength observations from the LSST Deep Drilling Fields, we measure the AGN fraction and estimate the BHOF across $0<z<1$. Applying a hierarchical Bayesian model, we find that the inferred BHOF remains $100%$ for host galaxy masses below 10⁹ M_ at lower redshifts. These findings are consistent with light-seed scenarios. Additionally, we computed the black hole masses for several galaxies in the W-CDF-S to test the mass-weighted black hole occupation distributions from semi-analytic models (SAM). Using a reduced-χ² analysis, we find that the data are consistent with the main-sequence accretion model regardless of the assumed seeding mechanism. These results provide new observational constraints on SMBH seeding and highlight the value of combining deep extragalactic surveys with probabilistic modeling.