Abstract
Abstract In 2014 the NGC 5548 Space Telescope and Optical Reverberation Mapping campaign discovered a two-month anomaly when variations in the absorption and emission lines decorrelated from continuum variations. During this time the soft X-ray part of the intrinsic spectrum had been strongly absorbed by a line-of-sight (LOS) obscurer, which was interpreted as the upper part of a disk wind. Our first paper showed that changes in the LOS obscurer produces the decorrelation between the absorption lines and the continuum. A second study showed that the base of the wind shields the broad emission-line region (BLR), leading to the emission-line decorrelation. In that study, we proposed the wind is normally transparent with no effect on the spectrum. Changes in the wind properties alter its shielding and affect the spectral energy distribution (SED) striking the BLR, producing the observed decorrelations. In this work we investigate the impact of a translucent wind on the emission lines. We simulate the obscuration using XMM-Newton, NuSTAR, and Hubble Space Telescope observations to determine the physical characteristics of the wind. We find that a translucent wind can contribute a part of the He ii and Fe Kα emission. It has a modest optical depth to electron scattering, which explains the fainter far-side emission in the observed velocity-delay maps. The wind produces the very broad base seen in the UV emission lines and may also be present in the Fe Kα line. Our results highlight the importance of accounting for the effects of such winds in the analysis of the physics of the central engine.
Highlights
The broad emission-line region (BLR) is closely associated with the central regions and the supermassive black hole (SMBH) in active galactic nuclei (AGNs)
We considered the total observed equivalent widths (EWs) of strong emission lines from the Space Telescope and Optical Reverberation Mapping (STORM) data (Goad et al 2016; Pei et al 2017) and the total luminosity of Fe Kα observed by XMM-Newton (Mehdipour et al 2015)
We have used Hubble Space Telescope (HST) and XMM-Newton observational constraints to derive a model of the equatorial obscurer
Summary
The broad emission-line region (BLR) is closely associated with the central regions and the supermassive black hole (SMBH) in active galactic nuclei (AGNs). At almost the same time, the continuum and narrow absorption lines decorrelated (Kriss et al 2019), the “absorption-line holiday.” These spectral holidays, along with the presence of an X-ray obscurer in our line of sight (LOS) to the SMBH (Kaastra et al 2014), distinguish the 2014 version of NGC 5548 from normal AGNs. There is no part of the standard AGN scenario that produces holidays, so clearly something fundamental is missing (Dehghanian et al 2019a, 2019b, hereafter D19a and D19b). As argued by D19b, the base of the wind forms an equatorial obscurer, filtering the spectral energy distribution (SED) before the ionizing photons strike the BLR, leading to the observed emission-line holiday. Both disk winds and broad Fe Kα emission are considered to be common properties of AGNs, and we propose that the SED filtering through the wind is too
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