Multi-wavelength study of the Seyfert 1 galaxy NGC 3783 with XMM-Newton

Free access article

Issue		A&A Volume 392, Number 2, September III 2002


Page(s)		453 - 467
Section		Extragalactic astronomy
DOI		http://dx.doi.org/10.1051/0004-6361:20020914

A&A 392, 453-467 (2002)
DOI: 10.1051/0004-6361:20020914

Multi-wavelength study of the Seyfert 1 galaxy NGC 3783 with XMM-Newton

A. J. Blustin¹, G. Branduardi-Raymont¹, E. Behar², J. S. Kaastra³, S. M. Kahn², M. J. Page¹, M. Sako⁴ and K. C. Steenbrugge³

¹ MSSL, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT, UK
² Department of Physics, Columbia University, 550 West 120th Street, New York, NY 10027, USA
³ SRON National Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
⁴ Caltech, Pasadena, CA 91125, USA

(Received 8 May 2002 / Accepted 14 June 2002)

Abstract
We present the analysis of multi-wavelength XMM-Newton data from the Seyfert galaxy NGC 3783, including UV imaging, X-ray and UV lightcurves, the 0.2-10 keV X-ray continuum, the iron K $\alpha$ emission line, and high-resolution spectroscopy and modelling of the soft X-ray warm absorber. The 0.2-10 keV spectral continuum can be well reproduced by a power-law at higher energies; we detect a prominent Fe K $\alpha$ emission line, with both broad and narrow components, and a weaker emission line at 6.9 keV which is probably a combination of Fe K $\beta$ and $\ion{Fe}{xxvi}$ . We interpret the significant deficit of counts in the soft X-ray region as being due to absorption by ionised gas in the line of sight. This is demonstrated by the large number of narrow absorption lines in the RGS spectrum from iron, oxygen, nitrogen, carbon, neon, argon, magnesium, silicon and sulphur. The wide range of iron states present in the spectrum enables us to deduce the ionisation structure of the absorbing medium. We find that our spectrum contains evidence of absorption by at least two phases of gas: a hotter phase containing plasma with a log ionisation parameter $\xi$ (where $\xi$ is in erg cm s $^{\rm -1}$ ) of 2.4 and greater, and a cooler phase with log $\xi$ centred around 0.3. The gas in both phases is outflowing at speeds of around 800 km s $^{\rm -1}$ . The main spectral signature of the cold phase is the Unresolved Transition Array (UTA) of M-shell iron, which is the deepest yet observed; its depth requires either that the abundance of iron, in the cold phase, is several times that of oxygen, with respect to solar abundances, or that the absorption lines associated with this phase are highly saturated. The cold phase is associated with ionisation states that would also absorb in the UV.

Key words: galaxies: active -- galaxies: Seyfert -- galaxies: individual (NGC 3783) -- X-rays: galaxies -- ultraviolet: galaxies -- techniques: spectroscopic

Offprint request: A. J. Blustin, ajb@mssl.ucl.ac.uk

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