scholarly journals Testing broad-line region models with reverberation mapping

2020 ◽  
Vol 494 (2) ◽  
pp. 1611-1621 ◽  
Author(s):  
Hagai Netzer
Keyword(s):  
Time Lag ◽  
Galactic Nuclei ◽  
Balmer Line ◽  
Broad Line ◽  
Escape Probability ◽  
Reverberation Mapping ◽  
Broad Line Region ◽  
Line Region ◽  
High Metallicity ◽  
Good Agreement

ABSTRACT New reverberation mapping (RM) measurements, combined with accurate luminosities and line ratios, provide strong constraints on the location of the line emitting gas in the broad-line region (BLR) of active galactic nuclei (AGNs). In this paper, I present new calculations of radiation pressure and magnetic pressure confined clouds and apply them to a ‘generic AGN’ and to NGC 5548. The new calculations are in good agreement with the observed lags of all broad emission lines, and with the luminosities of Ly α, C iv 1549, O vi 1035, and He ii 1640. They are also in reasonable agreement with the luminosities of Mg ii 2798 and the 1990 Å blend of C iii] and Si iii] lines for high-metallicity gas. They explain the changes in time-lag following an increase in continuum luminosity and their dependencies on the inner and outer boundaries of the BLR. They also predict very strong Balmer and Paschen continua with important implications to continuum RM experiments. However, the calculated Balmer and Paschen line luminosities are too weak, by factors of 2–5. This ‘Balmer line crisis’ was noted in several earlier works and is now confirmed and constrained by RM measurements that were not available in the past. It seems that present photoionization codes that use the escape probability formalism fail to correctly compute the Balmer line luminosities in high-density, large optical depth gas.

scholarly journals Reverberation Mapping Analysis of the Broad-Line Region in Seyfert Galaxy NGC 4151

1998 ◽  
Vol 188 ◽  
pp. 424-425
Author(s):  
S.J. Xue ◽  
F.Z. Cheng
Keyword(s):  
Emission Line ◽  
Time Lag ◽  
Seyfert Galaxy ◽  
Broad Line ◽  
Reverberation Mapping ◽  
Ngc 4151 ◽  
Broad Line Region ◽  
Spectroscopic Monitoring ◽  
Line Region ◽  
The Continuum

One of the primary goals of AGN variability studies has been to determine the size of broad-line region (BLR) through the reverberation mapping technique. In a recent international multiwavelength spectroscopic monitoring campaign, NGC 4151 has been observed intensively by ground-based telescopes for a period of over 2 months, with a typical temporal resolution of 1 day. The main result from this optical campaign is that finding the variation in the emission line flux (Hβ or Hα) lagging the continuum by 0-3 days (1993 campaign: Kaspi et al. 1996). This is in contrast to the past results in which a time lag of 9±2 days was found for the same emission line (1988 campaign: Maoz et al. 1991). Such a BLR “size problem” may be caused by a different variability timescale of the ionizing continuum or a real change in BLR gas distribution in the 5.5 yr interval between the two watch campaigns. In order to clarify which of the two possibilities is most likely the real case, we performed further reverberation analysis on both optical datasets.

scholarly journals Central Masses and Broad‐Line Region Sizes of Active Galactic Nuclei. II. A Homogeneous Analysis of a Large Reverberation‐Mapping Database

2004 ◽  
Vol 613 (2) ◽  
pp. 682-699 ◽  
Author(s):  
B. M. Peterson ◽  
L. Ferrarese ◽  
K. M. Gilbert ◽  
S. Kaspi ◽  
M. A. Malkan ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Broad Line ◽  
Reverberation Mapping ◽  
Broad Line Region ◽  
Line Region

scholarly journals Anomalous Broad-Line Region responses to continuum variability in Active Galactic Nuclei – I. Hβ variability

2021 ◽  
Author(s):  
C Martin Gaskell ◽  
Kayla Bartel ◽  
Julia N Deffner ◽  
Iris Xia
Keyword(s):  
Galactic Nuclei ◽  
Broad Line ◽  
Reverberation Mapping ◽  
Broad Line Region ◽  
Line Region ◽  
Rapid Changes ◽  
Optical Continuum ◽  
Ngc 5548 ◽  
Possible Cause

Abstract In the standard AGN reverberation-mapping model, variations in broad-line region (BLR) fluxes are predicted from optical continuum variability (taken as a proxy for the ionizing continuum) convolved with a response function that depends on the geometry. However, it has long been known that BLR variability can deviate from these predictions. We analyse both extensive long-term Hβ and continuum monitoring of NGC 5548 and a large sample of high-quality Hβ light curves of other AGNs to investigate the frequency and characteristics of anomalous responses of the BLR. We find that anomalies are very common and probably occur in every object. Onsets can be on a timescale only slightly longer than the light-crossing time and durations are of the order of the characteristic timescale of variability of the optical continuum to several times longer. Anomalies are larger when NGC 5548 is in a low state, but otherwise there is no correlation with continuum variability. There is abundant evidence for the optical continuum of AGNs varying independently of the higher-energy continua and this is sufficient to explain the anomalous responses of the total BLR flux. There are good reasons for believing that the frequent lack of correlation between spectral regions is due to anisotropic and non-axisymmetric emission. Rapid changes in line profiles and velocity-dependent lags are consistent with this. Motion of compact absorbing clouds across the line of sight is another possible cause of anomalies. The prevalence of anomalies should be considered when planning reverberation-mapping campaigns.

scholarly journals Steps toward Determination of the Size and Structure of the Broad‐Line Region in Active Galactic Nuclei. X. Variability of Fairall 9 from Optical Data

1997 ◽  
Vol 112 (2) ◽  
pp. 271-283 ◽  
Author(s):  
M. Santos‐Lleo ◽  
E. Chatzichristou ◽  
C. Mendes de Oliveira ◽  
C. Winge ◽  
D. Alloin ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Optical Data ◽  
Broad Line ◽  
Broad Line Region ◽  
Line Region ◽  
Size And Structure

scholarly journals Spectral Variability in Seyfert Galaxies

1987 ◽  
Vol 121 ◽  
pp. 161-167
Author(s):  
B.M. Peterson
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Seyfert Galaxies ◽  
Broad Line ◽  
Spectral Variability ◽  
Broad Line Region ◽  
Broad Emission ◽  
Line Region ◽  
Order Of Magnitude ◽  
Optical Continuum

Recent observations of spectral variability in active galactic nuclei have established the connection between the broad emission-line and optical continuum flux changes. The inferred size of the broad-line region is at least an order of magnitude smaller than conventional estimates based on photoionization models, which leads to new conclusions about the nature of the broad-line region.

scholarly journals Reverberation Mapping and Broad-Line Region Models

1997 ◽  
Vol 159 ◽  
pp. 138-145
Author(s):  
D. Maoz
Keyword(s):  
Broad Line ◽  
Future Directions ◽  
Reverberation Mapping ◽  
Broad Line Region ◽  
Line Region ◽  
Mapping Point

AbstractI review what we have learned about the BLR from reverberation mapping, point to some problems and complications that have emerged, and outline some future directions.

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