X-ray Absorption and Reflection in Active Galactic Nuclei

X-ray spectroscopy offers an opportunity to study the complex mixture of emitting and absorbing components in the circumnuclear regions of active galactic nuclei, and to learn about the accretion process that fuels AGN and the feedback of material to their host galaxies. We describe the spectral signatures that may be studied and review the X-ray spectra and spectral variability of active galaxies, concentrating on progress from recent Chandra, XMM-Newton and Suzaku data for local type 1 AGN. We describe the evidence for absorption covering a wide range of column densities, ionization and dynamics, and discuss the growing evidence for partial-covering absorption from data at energies > 10 keV. Such absorption can also explain the observed X-ray spectral curvature and variability in AGN at lower energies and is likely an important factor in shaping the observed properties of this class of source. Consideration of self-consistent models for local AGN indicates that X-ray spectra likely comprise a combination of absorption and reflection effects from material originating within a few light days of the black hole as well as on larger scales. It is likely that AGN X-ray spectra may be strongly affected by the presence of disk-wind outflows that are expected in systems with high accretion rates, and we describe models that attempt to predict the effects of radiative transfer through such winds, and discuss the prospects for new data to test and address these ideas.Comment: Accepted for publication in the Astronomy and Astrophysics Review. 58 pages, 9 figures. V2 has fixed an error in footnote

The iron K feature in narrow line Seyfert 1 galaxies: evidence for a P Cygni profile?

Narrow line Seyfert 1 galaxies are generally accreting at high fractions of the Eddington limit. They can show complex X-ray spectra, with a strong 'soft excess' below 2 keV and a sharp drop at ~7 keV. There is strong evidence linking the soft excess to either reflection or absorption from relativistic, partially ionized material close to the black hole. The reflection models can also simultaneously produce the 7-keV feature from fluorescent iron Kα line emission from the disc. Here we show that absorption can also produce a sharp feature at 7 keV from the P Cygni profile which results from absorption/scattering/emission of He- and H-like iron Kα resonance lines in the wind. We demonstrate this explicitly by fitting the iron feature seen in XMM-Newtondata from1H0707-495toa PCygni profile. The resulting column and ionization requiredtoproduce this feature are probably larger than those needed to produce the soft excess. Nonetheless, the absorbing material could still be a single structure with stratified ionization such as that produced by the ionization instability.</p