Testing the Seyfert unification theory: Chandra HETGS observations of NGC 1068

Free access article

Issue		A&A Volume 402, Number 3, May II 2003 First Science with the ODIN satellite


Page(s)		849 - 864
Section		Galactic structure and dynamics
DOI		http://dx.doi.org/10.1051/0004-6361:20021647

A&A 402, 849-864 (2003)
DOI: 10.1051/0004-6361:20021647

Testing the Seyfert unification theory: Chandra HETGS observations of NGC 1068

P. M. Ogle¹, T. Brookings¹, C. R. Canizares², J. C. Lee², ² and H. L. Marshall²

¹ UC Santa Barbara, Physics Department, Santa Barbara, CA 93106, USA
² MIT CSR, Cambridge, MA 02139, USA

(Received 15 May 2002 / Accepted 4 November 2002 )

Abstract
We present spatially resolved Chandra HETGS observations of the Seyfert 2 galaxy NGC 1068 . X-ray imaging and high resolution spectroscopy are used to test the Seyfert unification theory. Fe K $\alpha$ emission is concentrated in the nuclear region, as are neutral and ionized continuum reflection. This is consistent with reprocessing of emission from a luminous, hidden X-ray source by the obscuring molecular torus and X-ray narrow-line region (NLR). We detect extended hard X-ray emission surrounding the X-ray peak in the nuclear region, which may come from the outer portion of the torus. Detailed modeling of the spectrum of the X-ray NLR confirms that it is excited by photoionization and photoexcitation from the hidden X-ray source. K-shell emission lines from a large range of ionization states of H-like and He-like N, O, Ne, Mg, Al, Si, S, and $\ion{Fe}{xvii}$ -XXIV L-shell emission lines are modeled. The emission measure distribution indicates roughly equal masses at all observed ionization levels in the range $\log \xi = 1$ -3. We separately analyze the spectrum of an off-nuclear cloud. We find that it has a lower column density than the nuclear region, and is also photoionized. The nuclear X-ray NLR column density, optical depth, outflow velocity, and electron temperature are all consistent with values predicted by optical spectropolarimetry for the region which provides a scattered view of the hidden Seyfert 1 nucleus.

Key words: galaxies: active -- galaxies: individual: NGC 1068 -- X-rays: galaxies

Offprint request: P. M. Ogle, pmo@xmmom.physics.ucsb.edu

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