Fe II Curtain in Quasar Spectra
Katya Verner
Recently, the number of observational efforts to measure the Fe II /Mg II
emission ratios in quasars has increased, due to their potential to give a
clue to understanding of host galaxies and star formation in quasars.
With the goal to trace the iron abundance with the redshift we have
initiated the large Fe/Mg project in collaboration with Australia and Japan.
We will overview the previous efforts that done by others researches.
Also we present our recent developments and outline the potentials
for the future planning (ground based facilities and space missions)
connected to this project. In our first attempt to translate the observational
measurements into abundances, we use most sophisticated Fe II ion model
(830 levels) and HST/FOS spectra of quasar (PG 1626+554). We discuss the
observational errors in UV and optical parts spectra that influence flux
measurements. Then we demonstrate how to use Fe II (UV) band, Fe II (optical)
band and Mg II (UV) doublet fluxes to derive the iron abundance. The model
confirms that AGN continuum is greatly affected by Fe II. The Fe II simply
cannot be ignored in AGN studies. We will demonstrate that in spite of Fe II
complexity, both emission and absorption provide excellent diagnostic means in
astrophysical plasma. Since the wide range spectra can be obtained only for
low-z quasars, the Fe II observations are needed to calibrate the model before
applying in high-z quasars.