The Fe unresolved transition arrays (UTAs) produce prominent features in the ~15-17 Å wavelength range in the spectra of active galactic nuclei (AGNs). Here, we present new calculations of the energies and oscillator strengths of inner-shell lines from Fe XIV, Fe XV, and Fe XVI. These are crucial ions since they are dominant at inflection points in the gas thermal stability curve, and UTA excitation followed by autoionization is an important ionization mechanism for these species. We incorporate these, and data reported in previous papers, into the plasma simulation code Cloudy. This updated physics is subsequently employed to reconsider the thermally stable phases in absorbing media in AGNs. We show how the absorption profile of the Fe XIV UTA depends on density, due to the changing populations of levels within the ground configuration.

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Published in The Astrophysical Journal, v. 767, no. 2, 123, p. 1-12.

© 2013. The American Astronomical Society. All rights reserved. Printed in the U.S.A.

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G.J.F. acknowledges support by NSF (0908877; 1108928; and 1109061), NASA (10-ATP10-0053, 10-ADAP10-0073, and NNX12AH73G), JPL (RSA No 1430426), and STScI (HST-AR-12125.01, GO-12560, and HST-GO-12309). R.K. acknowledges support from the project VP1-3.1-ŠMM-07-K-02-013 funded by European Social Fund under the Global Grant measure. F.P.K. is grateful to AWE Aldermaston for the award of a William Penney Fellowship. P.v.H. acknowledges support from the Belgian Science Policy office through the ESA PRODEX programme.