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

Abstract

We analyze the results of long-term observations of broad-line region (BLR) in the Seyfert 1 galaxy NGC 5548 and provide a critical comparison with the predictions of a hydromagnetically-driven outflow model of Emmering, Blandford and Shlosman. We use this model to generate a time series of C IV line profiles that have responded to a time varying continuum. Our modifications to the model include cloud emission anisotropy, cloud obscuration, a CLOUDY-generated emissivity function and a narrow-line component which is added to the BLR component to generate 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 compared with the observations. Our model is able to reproduce the basic 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 emission line without varying the model parameters. The best fit model provides the effective size, the dominant geometry, the emissivity distribution and the 3D velocity field of the C IV BLR and constrains the mass of the central black hole to ∼ 3 × 10 7 M ⊙ . The inner part of the wind in NGC 5548 appears to be responsible for 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 red-side-first response in the relative velocity interval of 3, 000 km s −1 to 6, 000 km s −1 followed by the blue mid-wing and finally by the line core. Based on the comparison of data and model cross-correlation functions and one and two-dimensional transfer functions, we find that the rotating outflow model is compatible with observations of the BLR in NGC 5548.

Mass Loss from the Nuclei of Active Galaxies

“…The model was also applied to the formation and dynamics of BELR clouds by Emmering et al (1992) and Bottorff et al (1997). Emmering et al suggested that dusty material is initially rudiutively driven off the surface of the disk.…”

Hβ line width and the UV–X-ray spectra of luminous AGN

“…It has been suggested that Hβ and CIII] might arise from an optically-thick disk, and C IV and Lyα may be produced in a high-ionization wind (Murray & Chiang 1998, Bottorff et al 1997, Königl & Kartje 1994. If the emission lines are produced by different kinematic gas components, then a direct kinematic interpretation of their FWHM is not reasonable.…”

Gamma-ray opacity of the anisotropic stratified broad-line regions in blazars

“…The physical conditions in BLR are constrained by relative line intensities (see Osterbrock & Ferland (2006), sections 13.6 and 14.5, and references therein). BLR gas is often viewed as some sort of a wind produced by the accretion disc (see Bottorff et al 1997 and references therein) though there is strong observational evidence for inward-directed motions in BLRs (Doroshenko et al 2012;Grier et al 2013). The BLR size measured through reverberation mapping depends on the quasar UV luminosity LUV as RBLR,17 ∼ 1 × L 1/2 UV,45 (Kaspi et al 2007).…”