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Quasar Tomography: Unification of Echo Mapping and Photoionisation Models | | Keith Horne
; Kirk T Korista
; Michael R Goad
; | | Date: |
24 Oct 2002 | | Journal: | Mon.Not.Roy.Astron.Soc. 339 (2003) 367 | | Subject: | astro-ph | | Affiliation: | St.Andrews, Western Michigan, Southampton | | Abstract: | Reverberation mapping uses time-delayed variations in photoionised emission lines to map the geometry and kinematics of emission-line gas in active galactic nuclei. In previous work, the light travel time delay tau=R(1+cos(theta))/c and Doppler shift v give a 2-d map Psi(tau,v) for each emission line. Here we combine the velocity-delay information with photoionisation physics in a maximum entropy fit to the full reverberating spectrum F_lam(lam,t) to recover a 5-d map of the differential covering fraction f(R,theta,n,N,v), with n and N the density and column density of the gas clouds. We test the method for a variety of geometries (shells, rings, disks, clouds, jets) by recovering a 3-d map f(R,theta,n) from reverberations in 7 uv emission lines. The best test recovers a hollow shell geometry, defining R to 0.15 dex, n to 0.3 dex, and ionisation parameter U ~ 1/(n R^2) to 0.1 dex. The results are sensitive to the adopted distance and luminosity, suggesting that these parameters may be measurable as well. | | Source: | arXiv, astro-ph/0210539 | | Services: | Forum | Review | PDF | Favorites | |
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