Implications of infalling Fe II-emitting clouds in active galactic nuclei: Anisotropic properties

Gary J. Ferland, Chen Hu, Jian Min Wang, Jack A. Baldwin, Ryan L. Porter, Peter A.M. Van Hoof, R. J.R. Williams

Research output: Contribution to journalArticlepeer-review

75 Scopus citations


We investigate consequences of the discovery that Fe II emission in quasars, one of the spectroscopic signatures of "Eigenvector 1," may originate in infalling clouds. Eigenvector 1 correlates with the Eddington ratio L/L Edd so that Fe II/Hβ increases as L/L Edd increases. We show that the "force multiplier," the ratio of gas opacity to electron scattering opacity, is ∼103-104 in Fe II-emitting gas. Such gas would be accelerated away from the central object if the radiation force is able to act on the entire cloud. As had previously been deduced, infall requires that the clouds have large column densities so that a substantial amount of shielded gas is present. The critical column density required for infall to occur depends on L/L Edd, establishing a link between Eigenvector 1 and the Fe II/Hβ ratio. We see predominantly the shielded face of the infalling clouds rather than the symmetric distribution of emitters that has been assumed. The Fe II spectrum emitted by the shielded face is in good agreement with observations thus solving several long-standing mysteries in quasar emission lines.

Original languageEnglish
Pages (from-to)L82-L86
JournalAstrophysical Journal
Issue number1 PART 2
StatePublished - 2009


  • Accretion, accretion disks
  • Atomic processes
  • Galaxies: active
  • Line: formation
  • Quasars: emission lines

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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