SDSS J2125-0813: the evidence for the origination of optical FeII emission lines from accretion disk near central black hole

Abstract

We report on the radio quiet quasar SDSS J2125-0813 which obviously emits optical FeII emission lines and double-peaked broad Balmer emission lines. Using the accretion disk model for double-peaked broad low-ionization emission lines, we reproduce the composite line spectra at the optical band between 4100$Å$ and 5600$Å$. Broad FeII emission lines can be fit simultaneously with the broad H$β$ and MgI lines, such that all broad lines have an elliptical disk profile with the same disk parameters. This results indicates that the optical FeII emission lines originate from the accretion disk near the central black hole which produces the double-peaked broad Balmer emission lines. Furthermore, we find that the object has dimensionless accretion rate $\dot{m}\sim0.4-0.6$ which is much larger than accretion rate for ADAF mode, and that the energy budget of the accretion disk is enough to power the double-peaked broad Balmer emission lines.