James Webb Space Telescope Feed Post

Harvard ADS: JADES: A large population of obscured, narrow line AGN at high redshift

Paper abstract: We present the identification of 42 narrow-line active galactic nuclei (type-2 AGN) candidates in the two deepest observations of the JADES spectroscopic survey with JWST/NIRSpec. The spectral coverage and the depth of our observations allow us to select narrow-line AGNs based on both rest-frame optical and UV emission lines up to z=10. Due to the metallicity decrease of galaxies, at z>3 the standard optical diagnostic diagrams (N2-BPT or S2-VO87) become unable to distinguish many AGN from other sources of photoionisation. Therefore, we also use high ionisation lines, such as HeII\lambda4686, HeII\lambda1640, NeIV\lambda2422, NeV\lambda3420, and NV\lambda1240, also in combination with other UV transitions, to trace the presence of AGN. Out of a parent sample of 209 galaxies, we identify 42 type-2 AGN (although 10 of them are tentative), giving a fraction of galaxies in JADES hosting type-2 AGN of about 20\pm3\%, which does not evolve significantly in the redshift range between 2 and 10. The selected type-2 AGN have estimated bolometric luminosities of 10^{41.3-44.9} erg s^{-1} and host-galaxy stellar masses of 10^{7.2-9.3} M_{\odot}. The star formation rates of the selected AGN host galaxies are consistent with those of the star-forming main sequence. The AGN host galaxies at z=4-6 contribute ~8-30 \% to the UV luminosity function, slightly increasing with UV luminosity.