Optical emission line properties of a sample of the broad-line AGNs: the Baldwin effect and eigenvector 1

TL;DR

This study investigates how spectral properties of broad-line AGNs vary with different emission line ratios, revealing significant differences linked to starburst contributions and BLR kinematics, thus enhancing understanding of AGN emission mechanisms.

Contribution

It introduces a division of AGN samples based on emission line ratios, uncovering correlations that suggest a connection between BLR kinematics and ionization sources, which was not previously detailed.

Findings

Significant differences in spectral correlations based on [OIII]/Hbeta ratio.

Distinct relationships between broad Hbeta FWHM and luminosity in different subsamples.

Evidence for a link between BLR kinematics and photoionization source.

Abstract

We divide a sample of 302 type-1 AGNs into two subsamples based on the narrow line [OIII]/Hbeta_{NLR} ratio, since we expect that there will be a stronger starburst (HII region) contribution to the narrow line emission for R=log([OIII]/Hbeta_{NLR})<0.5. For the two samples we {find significant differences in correlations between} spectral properties of objects with $R<0.5$ and R>0.5. {We find similar differences when we divided the sample based on the FWHM ratios of [OIII] and broad Hbeta lines (R_1=log(FWHM[OIII]/FWHM Hbeta_broad)^>_<-0.8), i.e. similar correlations between R>0.5 and R_1<-0.8 subsamples from one side and R<0.5 and R_1>-0.8 subsamples from the other side.} The most interesting difference is in the correlation between the broad Hbeta FWHM and luminosity in the R<0.5 (R_1>-0.8) sample that indicates a connection between the BLR kinematics and photoionization source. We discuss possible effects which can cause such differences in spectral properties of two subsamples.