Expanded iron uta spectra - Probing the thermal stability limits in AGN clouds

G. J. Ferland, R. Kisielius, F. P. Keenan, P. A.M. Van Hoof, V. Jonauskas, M. L. Lykins, R. L. Porter, R. J.R. Williams

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


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.

Original languageEnglish
Article number123
JournalAstrophysical Journal
Issue number2
StatePublished - Apr 20 2013


  • X-rays: galaxies
  • atomic data
  • atomic processes
  • galaxies: active
  • line: formation
  • methods: numerical

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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