No Evidence for a Aystematic FEII Emission Line Redshift in Type 1 AGN

TL;DR

This study challenges previous claims by analyzing high-quality SDSS spectra and finds no evidence of a systematic FeII emission line redshift in Type 1 AGN, supporting the idea that FeII and Balmer lines originate from similar broad-line regions.

Contribution

The paper provides the first comprehensive analysis using median composites to refute claims of FeII redshift in Type 1 AGN, confirming that FeII emission shares kinematics with Balmer lines.

Findings

No systematic FeII redshift detected

FeII shift and width follow Hbeta in most sources

Supports similar origin of FeII and Balmer lines

Abstract

We test the recent claim by Hu et al. (2008) that FeII emission in Type 1 AGN shows a systematic redshift relative to the local source rest frame and broad-line Hbeta. We compile high s/n median composites using SDSS spectra from both the Hu et al. sample and our own sample of the 469 brightest DR5 spectra. Our composites are generated in bins of FWHM Hbeta and FeII strength as defined in our 4D Eigenvector 1 (4DE1) formalism. We find no evidence for a systematic FeII redshift and consistency with previous assumptions that FeII shift and width (FWHM) follow Hbeta shift and FWHM in virtually all sources. This result is consistent with the hypothesis that FeII emission (quasi-ubiquitous in type 1 sources) arises from a broad-line region with geometry and kinematics the same as that producing the Balmer lines.