Escaping the Bias: A More Complete View of AGN Demographics and Co-evolution from the ALPINE-CRISTAL

JWST has uncovered a growing population of high-redshift Active Galactic Nuclei (AGNs). A surprising narrative suggests early supermassive black holes (SMBHs) are "overmassive" relative to their host galaxies when compared to local relations. This challenges co-evolution models but is likely skewed by strong selection biases. We present new results from a search for broad-line AGNs within the ALPINE-CRISTAL-JWST survey, using deep JWST/NIRSpec IFU spectroscopy of 18 massive, star-forming galaxies at redshifts 4.4-5.7. We uncovered 7 AGN candidates by disentangling faint AGN signatures from outflows and host galaxy emission. One is a robust detection with a broad H-alpha line (width approx. 2800 km/s), while six others show broader components (widths 600-1600 km/s). Crucially, our SMBHs, with masses of 10^6 to 10^7.5 solar masses, lie close to or below local black hole mass-stellar mass relations. Simulations show this is a consequence of our survey design, which targets massive galaxies, making it sensitive to AGNs that follow local relations but are missed in other surveys. Our results highlight the critical role of selection bias and point to a large population of "normal" or even "undermassive" black holes, essential for a complete picture of AGN-galaxy co-evolution.