DYNAMICS OF BROAD EMISSION-LINE REGION IN NGC-5548 - HYDROMAGNETIC WIND MODEL VERSUS OBSERVATIONS

We analyze the results of long-term observations of the broad-line reg ion (BLR) in the Seyfert 1 galaxy NGC 5548 and provide a critical comp arison with the predictions of a hydromagnetically driven outflow mode l of Emmering, Blandford, & Shlosman. We use this model to generate a time series of C IV line profiles that have responded to a time-varyin g continuum. Our modifications to the model include cloud emission ani sotropy, cloud obscuration, a CLOUDY-generated emissivity function, an d a narrow-line component which is added to the BLR component to gener ate the total line profiles. The model is driven with continuum input based on the monitoring campaigns of NGC 5548 reported in Clavel et al . and Korista et al., and the line strengths, profiles, and lags are c ompared with the observations. Our model is able to reproduce the basi c features of C IV line variability in this active galactic nucleus, i .e., time evolution of the profile shape and strength of the C IV emis sion line without varying the model parameters. The best-fit model pro vides the effective size, the dominant geometry, the emissivity distri bution, and the three-dimensional velocity field of the C IV BER and c onstrains the mass of the central black hole to similar to 3 x 10(7) M .. The inner part of the wind in NGC 5548 appears to be responsible fo r the anisotropically emitted C IV line, while its outer part remains dusty and molecular, thus having similar spectral characteristics to a molecular torus, although its dynamics is fundamentally different. In addition, our model predicts a differential response across the C IV line profile, producing a redside-first response in the relative veloc ity interval of 3000 km s(-1) to 6000 km s(-1) followed by the blue mi d-wing and finally by the line core. Based on the comparison of data a nd model cross-correlation functions and one- and two-dimensional tran sfer functions, we find that the rotating outflow model is compatible with observations of the BLR in NGC 5548.