Missing FeII bump in faint JWST AGNs

To better understand the physical conditions in the broad-line regions (BLRs) of these early AGN, we used the optical FeII (4434-4684{AA}) and the broad Hbeta emission, and the ratio between their equivalent widths RFe, as a probe on a purposefully assembled sample.

Specifically, we gathered a sample of 31 high redshift (<z>=6.5) AGN, observed by JWST, with broad Hbeta detection both in the high and low luminosity regimes (respectively 14 faint AGN and 17 quasars), to investigate their optical FeII emission properties. In addition, we carefully selected control samples at lower z. We found that the population of faint AGN (log(L_Hb_/(erg/s))<~44) exhibits a significantly lower FeII emission than their local counterparts having a mean (median) R_Fe_<0.24 (0.12) versus R_Fe_~=0.90 (0.79) in the control sample.