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A. Kinkhabwala, M. Sako, E. Behar, F. Paerels, S. M. Kahn (Columbia), A. C. Brinkman, J. S. Kaastra (SRON), D. A. Liedahl (LLNL)
A new, unprecedented era in X-ray spectroscopy has been made possible by the recent launching of the {\small XMM-Newton} and Chandra satellites. X-ray spectra, roughly comparable in resolution to optical/UV spectra, have been taken for several Seyfert~2 galaxies, including the brightest one, NGC~1068. Despite the varying optical, UV, and IR spectra of these Seyfert~2, their X-ray spectra appear remarkably similar. Bright, narrow radiative recombination continua provide the ``smoking gun'' for relatively cool, recombining gas photoionized by the nuclear continuum. However, all spectra show deviations from the predicted spectrum of a purely recombining gas. These deviations could be due to significant photoexcitation or a separate, collisionally-driven gas component (e.~g., shock-heated gas in starburst regions). The observed anomalous strength of the higher-order ionic transitions provides unambiguous evidence for photoexcitation, whereas iron L-shell transitions provide useful diagnostics for determining the amount of collisionally-driven gas. Given the ability for robust discrimination of emission mechanisms, X-ray spectroscopy is uniquely well suited for probing the possible connection between Active Galactic Nucleus activity and star formation.
A.~K. would like to acknowledge support from an NSF fellowship.
The author(s) of this abstract have provided an email address for comments about the abstract: ali@phys.columbia.edu