JADES: comprehensive census of broad-line AGN from reionization to cosmic noon revealed by JWST

ABSTRACT The depth and coverage of the first years of James Webb Space Telescope observations have revealed low-luminosity active galactic nuclei (AGN) across a wide redshift range, shedding light on black hole (BH) assembly and feedback. We present our spectroscopic sample of 34 Type 1 AGN obtained from JADES survey data and spanning $1.5 < z < 9$. Our sample of AGN probes a BH mass range of $10^{6-9}$ M$_{\odot }$ at bolometric luminosities down to $10^{43}$ erg s$^{-1}$. Most of these AGN are hosted in low-mass ($M_{\star }\sim 10^8$ M$_{\odot }$) galaxies and are overmassive relative to the local $M_{BH}\!-\!M_{\star }$ relation, while remaining consistent with the local $M_{BH}$–$\sigma _*$ relation. The wide redshift range provided by our sample allows us to trace the emergence of local $M_{BH}$–$M_*$ scaling relation across cosmic time. Additionally, we explore the capability of narrow-line diagnostics in identifying Type 2 AGN and find that a significant fraction of our AGN would be missed by them due to low metallicity or lack of high-energy ionizing photons. We explore the UV luminosity function of AGN and their hosts and find that it is subject to significant cosmic variance and is also dependent on the AGN bolometric luminosity. Finally, we show that the electron scattering scenario recently proposed to explain broad Balmer lines is untenable on multiple grounds showing that there is no evidence of significant BH mass overestimation.