JADES: A large population of obscured, narrow-line active galactic nuclei at high redshift
Jan Scholtz, R. Maiolino, Francesco D’Eugenio, Emma Curtis-Lake, Stefano Carniani, S. Charlot, Mirko Curti, Maddie S. Silcock, Santiago Arribas, William Baker, Rachana Bhatawdekar, Kristan Boyett, Andrew J. Bunker, Jacopo Chevallard, Chiara Circosta, Daniel J. Eisenstein, Kevin Hainline, Ryan Hausen, Xihan Ji, Zhiyuan Ji, Benjamin D. Johnson, Nimisha Kumari, Tobias J. Looser, Jianwei Lyu, Michael V. Maseda, Eleonora Parlanti, Michele Perna, Marcia Rieke, Brant Robertson, Bruno Rodriguez Del, Fengwu Sun, Sandro Tacchella, Hannah Übler, Giacomo Venturi, Christina C. Williams, Christopher N. A. Willmer, Chris J. Willott, Joris Witstok
Abstract
We present the identification of 41 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 allowed us to select narrow-line AGN 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 used high ionisation lines, such as He II λ 4686, He II λ 1640, [Ne IV ] λ 2422, [Ne V ] λ 3420, and N V λ 1240, also in combination with other UV transitions, to trace the presence of AGN. Out of a parent sample of 209 galaxies, we identified 42 type-2 AGN (although ten of them are tentative), making the fraction of galaxies in JADES hosting type-2 AGN about 20 ± 5%, 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 ⊙ . 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 ∼18–30% to the UV luminosity function across different UV luminosity bins, increasing slightly with UV luminosity.