Physical conditions in the Seyfert galaxy NGC 2992

Mark G. Allen, Michael A. Dopita, Zlatan Tsvetanov, Ralph S. Sutherland

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This paper presents long-slit spectral maps of the bicone-shaped extended narrow-line region (ENLR) in the Seyfert galaxy NGC 2992. We investigate the physical properties of the ENLR via emission-line diagnostics and compare the observations to shock and photoionization models for the excitation mechanism of the gas. The line ratios vary as a function of position in the ENLR, and the loci of the observed points on line ratio diagrams are shown to be most consistent with shock + precursor model grids. We consider the energetics of a nuclear ionizing source for the ENLR and perform the q-test in which the rate of ionizing photons from the nucleus is inferred from measurements of the density and ionization parameter. The q-test is shown to be invalid in the case of NGC 2992 because of the limitations of the [S II] λ6717/λ6731 density diagnostic. The excitation of the gas is shown to be broadly consistent with the kinematics, with higher [N II] λ6583/Hα present in the more dynamically active region. We also show that the pressure associated with the X-ray-emitting plasma may provide a large fraction of the pressure required to power the ENLR via shocks.

Original languageEnglish
Pages (from-to)686-708
Number of pages23
JournalAstrophysical Journal
Issue number2 PART 1
Publication statusPublished - 1 Feb 1999
Externally publishedYes



  • Galaxies: active
  • Galaxies: individual (NGC 2992)
  • Galaxies: Seyfert

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Space and Planetary Science

Cite this

Allen, M. G., Dopita, M. A., Tsvetanov, Z., & Sutherland, R. S. (1999). Physical conditions in the Seyfert galaxy NGC 2992. Astrophysical Journal, 511(2 PART 1), 686-708.