MEOW: The Increase in the Obscured-AGN Fraction in Mid-IR from 0 ≤ z ≤ 6 with JWST MIRI

Abstract Obscured active galactic nuclei (AGNs) are often invoked to explain the rapid emergence of young quasars at high redshift and are crucial for building a complete census of AGN activity and black hole growth. The advent of the James Webb Space Telescope (JWST) extends the discovery space for obscured AGNs into the mid-IR with unprecedented precision through reprocessed dust emission. In this work, we use deep JWST Mid-Infrared Instrument (MIRI) imaging from the MIRI Early Obscured-AGN Wide Survey (MEOW), together with existing JWST Near Infrared Camera, spectroscopic, and Hubble Space Telescope imaging data, to identify a previously unrecognized population of obscured AGNs out to z  ≈ 6. Using spectral energy distribution modeling of the MIRI-detected sources, we identify 883 AGNs over an area of ~ 131 arcmin 2 and construct the AGN bolometric luminosity function, including both obscured and unobscured sources, across 5 redshift bins. We find an excess in AGN abundance relative to UV-selected AGN luminosity functions, indicating a substantial obscured population missed by optical/UV surveys, with the inferred obscured fraction increasing with redshift and reaching ∼98–99% in our highest-redshift bin, 4.5 z  < 6. We also find higher AGN abundances and obscured fractions than X-ray-based studies, consistent with a previously unrecognized population of heavily obscured, Compton-thick AGN revealed by mid-IR selection. These results suggest that a large fraction of supermassive black hole growth at early times occurs during heavily obscured phases largely inaccessible at other wavelengths.