Abstract
Considering the host galaxy contribution, a spectral decomposition method is used to reanalyzed the archive data of optical spectra for a narrow line Seyfert 1 galaxy, NGC 4051. The light curves of the continuum f λ (5100 Å), and Hβ, He ii, Fe ii emission lines are given. We find strong flux correlations between line emissions of Hβ, He ii, Fe ii and the continuum f λ (5100 Å). These low-ionization lines (Hβ, Fe ii, He ii) have “inverse” intrinsic Baldwin effects. Using the methods of the cross-correlation function and the Monte Carlo simulation, we find the time delays, with respect to the continuum, are \(3.45^{+12.0}_{-0.5}~\mbox{days}\) with the probability of 34 % for the intermediate component of Hβ, \(6.45^{+13.0}_{-1.0}~\mbox{days}\) with the probability of 65 % for the intermediate component of He ii. From these intermediate components of Hβ and He ii, the calculated central black hole masses are \(0.86^{+4.35}_{-0.33}\times 10^{6}\) and \(0.82^{+3.12}_{-0.45}\times 10^{6}~M_{\odot }\). We also find that the time delays for Fe ii are \(9.7^{+3.0}_{-5.0}~\mbox{days}\) with the probability of 36 %, \(8.45^{+1.0}_{-2.0}~\mbox{days}\) with the probability of 18 % for the total epochs and “subset 1” data, respectively. It seems that the Fe ii emission region is outside of the Hβ emission region.
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Acknowledgements
We thank an anonymous referee for suggestions that led to improvements in this paper. This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. This research has been supported by the National Science Foundations of China (No. 11173016; 11233003) and the National Basic Research Programme of China The 973 Programme (grant 2009CB824800).
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Yang, Z., Bian, WH. & Wang, Y. Optical spectral decomposition of NGC 4051. Astrophys Space Sci 348, 517–526 (2013). https://doi.org/10.1007/s10509-013-1566-3
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DOI: https://doi.org/10.1007/s10509-013-1566-3