The Ionized Gas and Nuclear Environment in NGC 3783. I. Time-Averaged 900 ks Chandra Grating Spectroscopy

Authors: Kaspi, S.1,2, Brandt, W.N.1, George, I.M.3,4, Netzer, H.2, Crenshaw, D.M.5, Gabel, J.R.6, Hamann, F.W.7, Kaiser, M.E.8, Koratkar, A.9, Kraemer, S.6, Kriss, G.A.8,9, Mathur, S.10, Mushotzky, R.F.3, Nandra, K.3,11, Peterson, B.M.10, Shields, J.C.12, Turner, T.J.3,4, Zheng, W.8,
Affiltns: 1Penn State Univ, 2Tel Aviv University, 3 LHEA, NASA/GSFC, 4 JCA, UMBC, 5 Georgia State University, 6 Catholic University of America, 7Univ. Florida, 8Johns Hopkins Univ, 9STScI, 10Ohio State Univ, 11 USRA, 12Ohio Univ
Journal: ApJ
Publn Date: in press

Summary

We present results from a 900 ks exposure of NGC 3783 with the High-Energy Transmission Grating Spectrometer on board the Chandra X-ray Observatory. The resulting X-ray spectrum has the best combination of signal-to-noise and resolution ever obtained for an AGN. This spectrum reveals absorption lines from H-like and He-like ions of N, O, Ne, Mg, Al, Si, and S. There are also possible absorption lines from H-like and He-like Ar and Ca. We also identify inner-shell absorption from lower-ionization ions such as Si VII-XII and S XII-XIV. The iron absorption spectrum is very rich; L-shell lines of Fe XVII-XXIV are detected, strong complex of M-shell lines, and probable resonance lines from Fe XXV. The absorption lines are blueshifted relative to the systemic velocity by a mean velocity of -590+/-150 km/s. We resolve many of the absorption lines, and their mean FWHM is 820+/-280 km/s. We do not find correlations between the velocity shifts or the FWHMs with the ionization potentials of the ions. Most absorption lines show asymmetry, having more extended blue wings than red wings. In O VII we have resolved this asymmetry to be from an additional absorption system at ~ -1300 km/s. The two X-ray absorption systems are consistent in velocity shift and FWHM with the ones identified in the UV lines of C IV, N V, and H I. Equivalent width measurements for all lines are given and column densities are calculated for several ions. We resolve the narrow Fe Kalpha line at 6398.2+/-3.3 eV to have a FWHM of 1720+/-360 km/s, which suggests that this narrow line may be emitted from the outer part of the broad line region or the inner part of the torus. We also detect a `Compton shoulder' redward of the narrow Fe Kalpha line which indicates it arises in cold, Compton-thick gas.

Figures: Fig1a Fig1b Fig2 Fig3 Fig4 Fig5 Fig6 Fig7 Fig8 Fig9 Fig10 Fig11 Fig12

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See Also

The Ionized Gas and Nuclear Environment in NGC 3783 papers:
I Time-averaged 900 ks Chandra Grating Spectroscopy
Kaspi, S., et al., 2002, ApJ, 574, 643
II Averaged HST/STIS and FUSE Spectra
Gabel, J.R., et al., 2003, ApJ, 583, 178
III Detection of a Decreasing Radial Velocity in an Intrinsic UV Absorber
Gabel, J.R., et al., 2003, ApJ, 595, 120
IV Variability and Modeling the 900 ks Chandra Spectrum
Netzer, H., et al., 2003, ApJ, 599, 933
V Variability and Modeling of the Intrinsic Ultraviolet Absorption
Gabel, J.R., 2005, ApJ, submitted