JWST CEERS and JADES Active Galaxies at z = 4-7 Violate the Local M •-M ⋆ Relation at >3σ: Implications for Low-mass Black Holes and Seeding Models

Abstract

JWST is revolutionizing our understanding of the high-z Universe by expanding the black hole horizon, looking farther and to smaller masses, and revealing the stellar light of their hosts. By examining JWST galaxies at z = 4-7 that host Hα-detected black holes, we investigate (i) the high-z M •-M ⋆ relation and (ii) the black hole mass distribution, especially in its low-mass range (M • ≲ 106.5 M ⊙). With a detailed statistical analysis, our findings conclusively reveal a high-z M •-M ⋆ relation that deviates at >3σ confidence level from the local relation. The high-z relation is log ( M • / M ⊙ ) = − 2.43 − 0.83 + 0.83 + 1.06 − 0.09 + 0.09 log ( M ⋆ / M ⊙ ) . Black holes are overmassive by ∼10-100× compared to their low-z counterparts in galactic hosts of the same stellar mass. This fact is not due to a selection effect in surveys. Moreover, our analysis predicts the possibility of detecting in high-z JWST surveys 5-15× more black holes with M • ≲ 106.5 M ⊙, and 10-30× more with M • ≲ 108.5 M ⊙, compared to local relation’s predictions. The lighter black holes preferentially occupy galaxies with a stellar mass of ∼107.5-108 M ⊙. We have yet to detect these sources because (i) they may be inactive (duty cycles 1%-10%), (ii) the host overshines the active galactic nucleus (AGN), or (iii) the AGN is obscured and not immediately recognizable by line diagnostics. A search of low-mass black holes in existing JWST surveys will further test the M •-M ⋆ relation. Current JWST fields represent a treasure trove of black hole systems at z = 4-7; their detection will provide crucial insights into their early evolution and coevolution with their galactic hosts. © 2023. The Author(s). Published by the American Astronomical Society.