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

Bottorff, Mark and Korista, Kirk T. and Shlosman, Isaac and Blandford, Roger D. (1997) Dynamics of Broad Emission‐Line Region in NGC 5548: Hydromagnetic Wind Model versus Observations. Astrophysical Journal, 479 (1). pp. 200-221. ISSN 0004-637X. doi:10.1086/303867.

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We analyze the results of long-term observations of the 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, & 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 themodel parameters. The best-fit model provides the effective size, the dominant geometry, the emissivity distribution, and the three-dimensional 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 3000 km s^(-1) to 6000 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.

Item Type:Article
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URLURL TypeDescription Paper
Blandford, Roger D.0000-0002-1854-5506
Additional Information:© 1997 The American Astronomical Society. Received 1996 July 18; accepted 1996 October 17. We thank Mitch Begelman, Chris Done, Matthias Dietrich, Julian Krolik, and Brad Peterson for valuable discussions, and the anonymous referee for helpful comments. We are grateful to Gary Ferland for assistance with the recent version of CLOUDY. This work was supported in part by NASA grants WKU-521751-94-08 and 521752-95-06 and NAGW-3839 (I. S.), NAG 3-223 (K. T. K.), and NSF grants AST 92-23370 and AST 95-29170 (R. D. B.).
Funding AgencyGrant Number
NSFAST 92-23370
NSFAST 95-29170
Subject Keywords:black hole physics - galaxies : active - galaxies : individual (NGC 5548) - galaxies : nuclei - galaxies : Seyfert - line : formation
Issue or Number:1
Record Number:CaltechAUTHORS:20190531-143942899
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Official Citation:Mark Bottorff et al 1997 ApJ 479 200
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:96015
Deposited By: Tony Diaz
Deposited On:31 May 2019 22:11
Last Modified:16 Nov 2021 17:17

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