Spatially resolved far-ultraviolet spectroscopy of the nuclear region of NGC 1068

Wei Zheng, Jun Xian Wang, Gerard A. Kriss, David Sahnow, Mark Allen, Michael Dopita, Zlatan Tsvetanov, Geoffrey Bicknell

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Abstract

We carry out high-resolution FUSE spectroscopy of the nuclear region of NGC 1068. The first set of spectra was obtainedwith a 30″ square aperture that collected all emission from the narrow-line region. The data reveal a strong broad O VI component of FWHM ∼3500 km s-1 and two narrow O VI λλ1031, 1037 components of ∼350 km s-1. The C III λ977 and N III λ991 emission lines in this spectrum can be fitted with a narrow component of FWHM ∼1000 km s-1 and a broad one of ∼2500 km s-1. Another set of seven spatially resolved spectra was made using a long slit of 1.25″ x 20″ at steps of ∼1″ along the axis of the emission-line cone. We find the following: (1) Major emission lines in the FUSE wavelength range consist of a broad and a narrow component. (2) There is a gradient in the velocity field for the narrow O VI component of ∼200 km s-1 from ∼2″ southwest of the nucleus to ∼4″ northeast. A similar pattern is also observed with the broad O VI component, with a gradient of ∼3000 km s-1. These are consistent with the HST STIS findings and suggest a biconical structure in which the velocity field is mainly radial outflow. (3) A major portion of the C III and N III line flux is produced in the compact core. They are therefore not effective temperature diagnostics for the conical region. (4) The best-fit UV continuum suggests virtually no reddening, and the He II I(λ1640)/ I(λ1085) ratio suggests a consistently low extinction factor across the cone. At ∼2″ northeast of the nucleus there is a region characterized by (a) a strong Lyα flux but normal C IV flux, (b) a broad O VI line, and (c) a significantly enhanced C III flux.

Original languageEnglish
Pages (from-to)881-891
Number of pages11
JournalAstrophysical Journal
Volume686
Issue number2
DOIs
Publication statusPublished - 20 Oct 2008
Externally publishedYes

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Keywords

  • Galaxies: active
  • Galaxies: individual (NGC 1068)
  • Galaxies: Seyfert

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Zheng, W., Wang, J. X., Kriss, G. A., Sahnow, D., Allen, M., Dopita, M., Tsvetanov, Z., & Bicknell, G. (2008). Spatially resolved far-ultraviolet spectroscopy of the nuclear region of NGC 1068. Astrophysical Journal, 686(2), 881-891. https://doi.org/10.1086/591547