  The unresolved transition array (UTA) of iron M-shell ions is a prominent
absorption feature in the X-ray spectrum of many active galactic nuclei (AGNs).
Modeling photoionized plasmas in attempt to match the observed silicon and
oxygen lines fail to predict the level of ionization of iron as inferred by
this feature. It is suggested that the discrepancy is due to underestimation of
the low-temperature dielectronic recombination rates for iron M-shell ions.
Modified ionization balance calculations, based on new (guessed) atomic data,
support this idea. The results are shown and compared to the global properties
of several observed UTAs. Implications for AGN absorbing gas are discussed
including an analysis of the ionization parameter distribution in such sources.
The need for real calculations of such atomic data is stressed.
