The FeII Optical Emission in AGN

Abstract

We investigated the optical FeII emission in a sample of about 215 low-redshift AGN (quasars and luminous Seyfert 1 galaxies). We find that a scaled and broadened FeII template based on the I Zw 1 spectrum can satisfactorily model the FeII emission in almost all sources in our sample. We confirm that FWHM H$β$ and FeII$λ$4570 are strongly correlated. The correlation is different for sources with FWHM(H$β$) greater than or less than $\sim$4000 km s$^{-1}$. Sources with FWHM H$β$$\leq$ 4000 km s$^{-1}$ (Population A) show no difference between FWHM H$β$ and FeII while sources with FWHM(H$β$) $\geq$ 4000 km s$^{-1}$ (Population B) show FWHM FeII that is systematically smaller than FWHM H$β$. This may be telling us that FeII emission in Pop. B sources comes from only the outermost part of the H$β$\ emitting region where the degree of ionization is lowest.