Improved Fe II emission line models for AGN using new atomic datasets
  Understanding the Fe II emission from Active Galactic Nuclei (AGN) has been a
grand challenge for many decades. The rewards from understanding the AGN
spectra would be immense, involving both quasar classification schemes such as
"Eigenvector 1" and tracing the chemical evolution of the cosmos. Recently,
three large Fe II atomic datasets with radiative and electron collisional rates
have become available. We have incorporated these into the spectral synthesis
code Cloudy and examine predictions using a new generation of AGN Spectral
Energy Distribution (SED), which indicates that the UV emission can be quite
different depending on the dataset utilized. The Smyth et al dataset better
reproduces the observed Fe II template of the I ZW 1 Seyfert galaxy in the UV
and optical regions, and we adopt these data. We consider both thermal and
microturbulent clouds and show that a microturbulence of $\approx$ 100 km/s
reproduces the observed shape and strength of the so-called Fe II "UV bump".
Comparing our predictions with the observed Fe II template, we derive a typical
cloud density of $10^{11}$ cm$^{-3}$ and photon flux of $10^{20}$ cm$^{-2}$
s$^{-1}$, and show that these largely reproduce the observed Fe II emission in
the UV and optical. We calculate the $I$(Fe II)/$I$(Mg II) emission-line
intensity ratio using our best-fitting model and obtain log($I$(Fe II)/$I$(Mg
II)) $\sim$ 0.7, suggesting many AGNs have a roughly solar Fe/Mg abundance
ratio. Finally, we vary the Eddington ratio and SED shape as a step in
understanding the Eigenvector 1 correlation.
