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arXiv · 0806.4641

Spatially Resolved Far-Ultraviolet Spectroscopy of the Nuclear Region of NGC 1068

W. Zheng·J. Wang·G. A. Kriss·D. Sahnow·M. Allen·M. Dopita·Z. Tsvetanov·G. 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 obtained with a 30" square aperture that collects all emission from the narrow-line region. The data reveal a strong broad OVI component of FWHM ~3500 kms-1 and two narrow OVI 1031/1037 components of ~350 kms-1. The CIII 977 and NIII 991 emission lines in this spectrum can be fitted with a narrow component of FWHM ~1000 kms-1 and a broad one of ~2500 kms-1. Another set of seven spatially resolved spectra were made using a long slit of 1.25" X 20", at steps of ~1" along the axis of the emission-line cone. We find that (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 OVI component of ~200 kms-1 from ~2" southwest of the nucleus to ~4" northeast. A similar pattern is also observed with the broad OVI component, with a gradient of ~3000 kms-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 CIII and NIII line flux is produced in the compact core. They are therefore not effective temperature diagnostics for the conical region; and (4) The best-fitted UV continuum suggests virtually no reddening, and the HeII 1085/1640 ratio suggests a consistently low extinction factor across the cone.

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W. Zheng, J. Wang, G. A. Kriss, D. Sahnow, M. Allen, M. Dopita, Z. Tsvetanov, G. Bicknell. 2008-06-28. Spatially Resolved Far-Ultraviolet Spectroscopy of the Nuclear Region of NGC 1068. https://doi.org/10.1086/591547

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