Taming the derivative: diagnostics of the continuum and H$\beta$ emission in a prototypical Population B active galaxy

Abstract

We report preliminary results on the analysis of the continuum and H$\beta$ light curves of the type-1 active galactic nucleus (AGN) NGC 5548. We notice a clear signature of shallowing in the trend between the H$\beta$ and the continuum luminosities. We attempt the recovery of this observed H$\beta$ emission trend as a response to large continuum flux increase using CLOUDY photoionization simulations. We explore a wide range in the physical parameters space for modelling the H$\beta$ emission from the broad-line region (BLR) appropriate for this source. We employ a constant density, single cloud model approach in this study and successfully recover the observed shallowing of the H$\beta$ emission with respect to the rising AGN continuum. With our modelling, we are able to provide constraints on the local BLR cloud density and recover the BLR distances (from the continuum source) consistent with the H$\beta$ reverberation mapping estimates. We further discuss the implications of the BLR covering factor and their sizes on recovering the observed trend.

arXiv comment10 pages, 7 figures, accepted version after proofs in Astronomische Nachrichten (Special Issue, 13th Serbian Conference on Spectral Line Shapes in Astrophysics)

References in corpus (38)

• The Low-Luminosity End of the Radius-Luminosity Relationship for Active Galactic Nuclei
• Systematic Effects in Measurement of Black Hole Masses by Emission-Line Reverberation of Active Galactic Nuclei: Eddington Ratio and Inclination
• ULySS: A Full Spectrum Fitting Package
• The diversity of quasars unified by accretion and orientation
• Locally Optimally Emitting Clouds and the Origin of Quasar Emission Lines
• Eigenvector 1: An Optimal Correlation Space for Active Galactic Nuclei
• Groups of Galaxies in the Two Micron All-Sky Redshift Survey
• Supermassive Black Holes with High Accretion Rates in Active Galactic Nuclei. IX 10 New Observations of Reverberation Mapping and Shortened H$\beta$ Lags
• Steps Toward Determination of the Size and Structure of the Broad-Line Region in Active Galactic Nuclei. XVI. A Thirteen-Year Study of Spectral Variability in NGC 5548
• Anatomy of the AGN in NGC 5548: I. A global model for the broadband spectral energy distribution
• Space Telescope and Optical Reverberation Mapping Project. I. Ultraviolet Observations of the Seyfert 1 Galaxy NGC 5548 with the Cosmic Origins Spectrograph on Hubble Space Telescope
• The Origin of Fe II Emission in AGN
• Space Telescope and Optical Reverberation Mapping Project. V. Optical Spectroscopic Campaign and Emission-Line Analysis for NGC 5548
• Locally Optimally-Emitting Clouds and the Variable Broad Emission Line Spectrum of NGC 5548
• The Quasar Main Sequence explained by the combination of Eddington ratio, metallicity and orientation
• Modelling of the quasar main sequence in the optical plane
• Evidence for periodicity in 43 year-long monitoring of NGC 5548
• Space Telescope and Optical Reverberation Mapping Project. IV. Anomalous behavior of the broad ultraviolet emission lines in NGC 5548
• Space Telescope and Optical Reverberation Mapping Project. IX. Velocity-Delay Maps for Broad Emission Lines in NGC 5548
• Long-term variability of the optical spectra of NGC 4151: I. Light curves and flux correlations
• Reverberation Mapping of the Broad-line Region in NGC 5548: Evidence for Radiation Pressure?
• Profile variability of the H-alpha and H-beta broad emission lines in NGC5548
• Interpreting broad emission-line variations I : Factors influencing the emission-line response
• Photoionized HBeta Emission in NGC 5548: It Breathes!
• High metal content of highly accreting quasars
• Anatomy of the AGN in NGC 5548: III. The high-energy view with NuSTAR and INTEGRAL
• Low-Ionization Emission Regions in Quasars: Gas Properties Probed with Broad O I and Ca II Lines
• Space Telescope and Optical Reverberation Mapping Project. X. Understanding the Absorption-Line Holiday in NGC 5548
• Improved Fe II emission line models for AGN using new atomic datasets
• Reverberation and photoionization estimates of the Broad Line Region Radius in Low-z Quasars
• The CaFe Project: Optical Fe II and Near-Infrared Ca II triplet emission in active galaxies -- simulated EWs, the co-dependence of cloud sizes and metal content
• OI and CaII observations in intermediate redshift quasars
• The CaFe Project: Optical Fe II and Near-Infrared Ca II triplet emission in active galaxies: (I) Photoionization modelling
• Variability of Optical \ion{Fe}{ii} Complex in Narrow-Line Seyfert 1 Galaxy NGC 4051
• Revealing the Broad Line Region of NGC 1275: The Relationship to Jet Power
• Interpreting broad emission-line variations II: Tensions between luminosity, characteristic size and responsivity
• Anomalous Broad-Line Region Responses to Continuum Variability in Active Galactic Nuclei. I. H$\beta$ Variability
• Efficiency tests for estimating the gas and stellar population parameters in Type 2 objects

Cited by in corpus (5)

• Broad-line region in active galactic nuclei: Dusty or dustless?
• Unveiling the quasar main sequence: illuminating the complexity of active galactic nuclei and their evolution
• Application of the FRADO model of BLR formation to the Seyfert galaxy NGC 5548 and the first step toward determining the Hubble constant
• HALO I: Photometric continuum reverberation mapping of Fairall 9
• Rarefied Broad-Line Regions in Active Galactic Nuclei: Anomalous Responses in Reverberation Mapping and Implications for Weak Emission-Line Quasars