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

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)


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
Pages (from-to)1-12
JournalAstrophysical Journal
Early online date04 Apr 2013
Publication statusPublished - 20 Apr 2013


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

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics


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