James Webb Space Telescope Feed Post

Harvard ADS: Narrow line AGN selection in CEERS: spectroscopic selection, physical properties, X-ray and radio analysis

Paper abstract: In this work, we spectroscopically select narrow-line AGN (NLAGN) among the ~ 300 publicly available medium-resolution spectra of the CEERS Survey. Using both traditional and newly identified emission line NLAGN diagnostics diagrams, we identified 52 NLAGN at 2<~ z<~ 9 on which we performed a detailed multiwavelength analysis. We also identified 4 new z<~ 2 broad-line AGN (BLAGN), in addition to the 8 previously reported high-z BLAGN. We found that the traditional BPT diagnostic diagrams are not suited to identify high-z AGN, while most of the high-z NLAGN are selected using the recently proposed AGN diagnostic diagrams based on the [OIII]\lambda4363 auroral line or high-ionization emission lines. We compared the emission line velocity dispersion and the obscuration of the sample of NLAGN with those of the parent sample without finding significant differences between the two distributions, suggesting a population of AGN heavily buried and not significantly impacting the host galaxies' physical properties, as further confirmed by SED-fitting. The bolometric luminosities of the high-z NLAGNs selected in this work are well below those sampled by surveys before JWST, potentially explaining the weak impact of these AGN. Finally, we investigate the X-ray properties of the selected NLAGN and of the sample of high-z BLAGN. We find that all but 4 NLAGN are undetected in the deep X-ray image of the field, as well as all the high-z BLAGN. We do not obtain a detection even by stacking the undetected sources, resulting in an X-ray weakness of ~ 1-2 dex from what is expected based on their bolometric luminosities. To discriminate between a heavily obscured AGN scenario or an intrinsic X-ray weakness of these sources, we performed a radio stacking analysis, which did not reveal any detection leaving open the questions about the origin of the X-ray weakness.