Dynamics of Broad Emission‐Line Region in NGC 5548: Hydromagnetic Wind Model versus Observations

We analyze the results of long-term observations of broad-line region (BLR)in the Sy1 galaxy NGC 5548 and provide a critical comparison with thepredictions of a hydromagnetically-driven outflow model of Emmering, Blandfordand Shlosman. This model was used to generate a time series of CIV lineprofiles that have responded to a time varying continuum. The model includescloud emission anisotropy, cloud obscuration, a CLOUDY-generated emissivityfunction and a narrow-line component used to generate the line profiles, and isdriven with continuum input based on the monitoring campaigns of NGC 5548. Theline strengths, profiles and lags are compared with the observations. Itreproduces the basic features of CIV line variability in this AGN withoutvarying the model parameters. The best fit model provides the effective size,the dominant geometry, the emissivity distribution and the 3D velocity field ofthe CIV BLR and constrains the mass of the central BH. The inner part of thewind appears to be responsible for the anisotropically emitted CIV line, whileits outer part remains dusty and molecular, thus having similar spectralcharacteristics to a molecular torus, although its dynamics is fundamentallydifferent. In addition, our model predicts a differential response across theCIV line profile, producing a red-side-first response in the mid-wings followedby the blue mid-wing and by the line core. Based on the comparison of data andmodel cross-correlation functions and 1D and 2D transfer functions, we findthat the rotating outflow model is compatible with observations of the BLR inNGC 5548.Comment: 50 pages, TeX, 14 figures. Also available as compressed postscript at ftp://gradj.pa.uky.edu/shlosman/ngc5548 . Accepted for publication in Ap