The properties of optical FeII emission lines of AGN with double-peaked broad emission lines

Abstract

We study the FeII properties of double-peaked broad low-ionization emission line AGN (dbp emitters) using a sample of 27 dbp emitters from SDSS (DR4), with mean value $σ_{Hα_{B}}\sim3002\pm139{\rm km\cdot s^{-1}}$. Our first result is that the line spectra in the wavelength range from 4100$Å$ to 5800$Å$ can be best fitted by an elliptical accretion disk model, assuming the same double-peaked line profiles for H$β$, FeII, H$γ$ and HeII$\lambda4686Å$ as that of double-peaked broad H$α$ for all the 27 dbp emitters, except the object SDSS J2125-0813 which we have discussed in a previous paper. The best fitted results indicate that the optical FeII emission lines of dbp emitters originate from the same region in the accretion disk where the double-peaked Balmer emission lines originate. Some correlations between FeII emission lines and the other broad emission lines for normal AGN can be confirmed for dbp emitters. However, these results should be taken with caution due to the small number of objects and the bias in selecting strong FeII emitters. We show that for dbp emitters, BH masses seems to have more influence on FeII properties than dimensionless accretion rate. We also find that the dbp emitters in the sample are all radio quiet quasars except one dbp emitter with $R_r> 1$ according to the definition by Ivezi$\rm{\acute{c}}$ et al. (2002) and 6 objects undiscovered by FIRST.