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Session 98 - AGN-Absorption/Emission.
Display session, Thursday, January 16
Metropolitan Ballroom,
The launch of the Infrared Space Observatory and new atomic data calculations have opened a window to the study of high ionization gas in active galactic nuclei (AGN). We present the results of large grids of photoionization simulations of the ``coronal line'' region in AGN, employing new atomic data from the Opacity and Iron Projects. Our computations span 8 orders of magnitude in gas density and 14 orders of magnitude in ionizing flux in an effort to identify the optimal conditions in which these lines form. We show that coronal lines form at distances from just outside the broad line region to \sim 400L_43.5^1/2 pc, in gas with ionization parameter -2.2 \lesssim \log U(H) \lesssim 1.0, corresponding to gas densities of 10^2 to 10^8.75 cm^-3, with electron temperatures \sim 12,000 K -- 150,000 K. A large range of distances from the central source implies significant line width variation among the coronal lines. We identify several line ratios which could be used to measure relative abundances, and we use these to show that the coronal line gas is likely to be dust free.
