JWST CEERS and JADES Active Galaxies at z = 4–7 Violate the Local M <sub>•</sub>–M <sub>⋆</sub> Relation at >3σ: Implications for Low-mass Black Holes and Seeding Models
Fabio Pacucci, Bao Nguyen, Stefano Carniani, R. Maiolino, Xiaohui Fan
Abstract
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 H α -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 • ≲ 10 6.5 M ⊙ ). With a detailed statistical analysis, our findings conclusively reveal a high- z M • – M ⋆ relation that deviates at >3 σ confidence level from the local relation. The high- z relation is <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>•</mml:mo> </mml:mrow> </mml:msub> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:mspace width="0.25em"/> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> <mml:mo stretchy="false">)</mml:mo> <mml:mo>=</mml:mo> <mml:mo>−</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>2.43</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.83</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.83</mml:mn> </mml:mrow> </mml:msubsup> <mml:mo>+</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>1.06</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.09</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.09</mml:mn> </mml:mrow> </mml:msubsup> <mml:mi>log</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⋆</mml:mo> </mml:mrow> </mml:msub> <mml:mrow> <mml:mo stretchy="true">/</mml:mo> </mml:mrow> <mml:mspace width="0.25em"/> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> <mml:mo stretchy="false">)</mml:mo> </mml:math> . 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 • ≲ 10 6.5 M ⊙ , and 10–30× more with M • ≲ 10 8.5 M ⊙ , compared to local relation’s predictions. The lighter black holes preferentially occupy galaxies with a stellar mass of ∼10 7.5 –10 8 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.