Interpreting broad emission-line variations I : Factors influencing the emission-line response

Abstract

We investigate the sensitivity of the measured broad emission-line responsivity dlog f_line/dlog f_cont to continuum variations in the context of straw-man BLR geometries of varying size with fixed BLR boundaries, and for which the intrinsic emission-line responsivity is known a priori. We find for a generic emission-line that the measured responsivity, delay and maximum of the cross-correlation function are correlated for characteristic continuum variability timescales T_char less than the maximum delay for that line tau_max(line) for a particular choice of BLR geometry and observer orientation. The above correlations are manifestations of geometric dilution arising from reverberation effects within the spatially extended BLR. When present, geometric dilution reduces the measured responsivity, delay and maximum of the cross-correlation function. We also find that the measured responsivity and delay show a strong dependence on light-curve duration, with shorter campaigns resulting in smaller than expected values, and only a weak dependence on sampling rate. The observed strong negative correlation between continuum level and line responsivity found in previous studies cannot be explained by differences in the sampling pattern, light-curve duration or in terms of purely geometrical effects. To explain this and to satisfy the observed positive correlation between continuum luminosity and BLR size in an individual source, the responsivity-weighted radius must increase with increasing continuum luminosity. For a BLR with fixed inner and outer boundaries this requires radial surface emissivity distributions which deviate significantly from a simple power-law, and in such a way that the intrinsic emission-line responsivity increases toward larger BLR radii, in line with photoionisation calculations.

arXiv comment21 pages, 17 figures, accepted for publication in MNRAS July 2014

References in corpus (30)

• Are the Variations in Quasar Optical Flux Driven by Thermal Fluctuations?
• Modeling the Time Variability of SDSS Stripe 82 Quasars as a Damped Random Walk
• Biases in Virial Black Hole Masses: An SDSS Perspective
• Non-linear X-ray variability in X-ray binaries and active galaxies
• Reverberation Measurements of the Inner Radius of the Dust Torus in Nearby Seyfert 1 Galaxies
• The Lick AGN Monitoring Project: Broad-Line Region Radii and Black Hole Masses from Reverberation Mapping of Hbeta
• The Radius-Luminosity Relationship for Active Galactic Nuclei: The Effect of Host-Galaxy Starlight on Luminosity Measurements
• Quantifying Quasar Variability As Part of a General Approach To Classifying Continuously Varying Sources
• An Alternative Approach To Measuring Reverberation Lags in Active Galactic Nuclei
• Locally Optimally Emitting Clouds and the Origin of Quasar Emission Lines
• What the Optical Recombination Lines Can Tell Us About the Broad Line Regions of Active Galactic Nuclei
• On the Reliability of Cross Correlation Function Lag Determinations in Active Galactic Nuclei
• 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
• The Variable Diffuse Continuum Emission of Broad Line Clouds
• Systematic Uncertainties in Black Hole Masses Determined from Single Epoch Spectra
• The Size of the Narrow-Line Emitting Region in the Seyfert 1 Galaxy NGC 5548 from Emission-Line Variability
• The broad emission-line region: the confluence of the outer accretion disc with the inner edge of the dusty torus
• Locally Optimally-Emitting Clouds and the Variable Broad Emission Line Spectrum of NGC 5548
• NGC 5548 in a Low-Luminosity State: Implications for the Broad-Line Region
• The Impact of the Uncertainty in Single-Epoch Virial Black Hole Mass Estimates on the Observed Evolution of the Black Hole - Bulge Scaling Relations
• Photoionized HBeta Emission in NGC 5548: It Breathes!
• Variability of Fe II Emission Features in the Seyfert 1 Galaxy NGC 5548
• Virial Masses of Black Holes from Single Epoch Spectra of AGN
• An Intrinsic Baldwin Effect in the H-beta Broad Emission Line in the Spectrum of NGC 5548
• The orientation dependence of quasar single-epoch black hole mass scaling relationships
• Variability of accretion flow in the core of the Seyfert galaxy NGC 4151
• Is the slope of the intrinsic Baldwin effect constant?
• Quasar Tomography: Unification of Echo Mapping and Photoionisation Models
• Magnetohydrodynamic stability of broad line region clouds
• The non-constant slope of the CIV Baldwin effect in NGC 4151

Cited by in corpus (40)

• Supermassive Black Holes with High Accretion Rates in Active Galactic Nuclei. IV. H$\beta$ Time Lags and Implications for Super-Eddington Accretion
• Supermassive Black Holes with High Accretion Rates in Active Galactic Nuclei. IX 10 New Observations of Reverberation Mapping and Shortened H$\beta$ Lags
• The Lick AGN Monitoring Project 2011: Spectroscopic Campaign and Emission-Line Light Curves
• Supermassive Black Holes with High Accretion Rates in Active Galactic Nuclei. V. A New Size-Luminosity Scaling Relation for the Broad-Line Region
• Space Telescope and Optical Reverberation Mapping Project. V. Optical Spectroscopic Campaign and Emission-Line Analysis for NGC 5548
• Quantifying the impact of variable BLR diffuse continuum contributions on measured continuum inter-band delays
• Quantifying the Diffuse Continuum Contribution of BLR Clouds to AGN Continuum Inter-band Delays
• Supermassive Black Holes with High Accretion Rates in Active Galactic Nuclei. VIII. Structure of the Broad-Line Region and Mass of the Central Black Hole in Mrk 142
• Space Telescope and Optical Reverberation Mapping Project. IV. Anomalous behavior of the broad ultraviolet emission lines in NGC 5548
• Continuum Reverberation Mapping of the Accretion Disks in Two Seyfert 1 Galaxies
• The Sloan Digital Sky Survey Reverberation Mapping Project: The H$\beta$ Radius-Luminosity Relation
• Broad Hbeta Emission-Line Variability in a Sample of 102 Local Active Galaxies
• What does Civλ1549 tell us about the physical driver of the Eigenvector Quasar Sequence?
• Understanding Broad Mg II Variability in Quasars with Photoionization: Implications for Reverberation Mapping and Changing-Look Quasars
• Space Telescope and Optical Reverberation Mapping Project. VIII. Time Variability of Emission and Absorption in NGC 5548 Based on Modeling the Ultraviolet Spectrum
• Constraints on the broad line region from regularized linear inversion: Velocity-delay maps for five nearby active galactic nuclei
• Black hole mass estimates in quasars - A comparative analysis of high- and low-ionization lines
• The most powerful quasar outflows as revealed by the Civ λ1549 resonance line
• Reverberation Mapping of the Broad Line Region: application to a hydrodynamical line-driven disk wind solution
• Evidence for Two Distinct Broad-Line Regions from Reverberation Mapping of PG 0026+129
• Monitoring AGNs with Hβ Asymmetry. II. Reverberation Mapping of Three Seyfert Galaxies Historically Displaying Hβ Profiles with Changing Asymmetry: Mrk 79, NGC 3227, and Mrk 841
• Interpretation of Departure from the Broad Line Region Scaling in Active Galactic Nuclei
• Broad-line Region of the Quasar PG 2130+099 from a Two-Year Reverberation Mapping Campaign with High Cadence
• Kinematic signatures of reverberation mapping of close binaries of supermassive black holes in active galactic nuclei
• What controls the UV-to-X-ray continuum shape in quasars?
• The intrinsic Baldwin effect in broad Balmer lines of six long-term monitored AGNs
• The reverberation signatures of rotating disc winds in active galactic nuclei
• Intermediate-line Emission in AGNs: The Effect of Prescription of the Gas Density
• Interpreting broad emission-line variations II: Tensions between luminosity, characteristic size and responsivity
• Quasar emission lines as probes of orientation: implications for disc wind geometries and unification
• Spectroastrometry and Reverberation Mapping: the Mass and Geometric Distance of the Supermassive Black Hole in the Quasar 3C 273
• Relation between the variations in the MgII $\lambda 2798$ emission-line and the 3000 Å continuum
• The SDSS-V Black Hole Mapper Reverberation Mapping Project: Unusual Broad-Line Variability in a Luminous Quasar
• Taming the derivative: diagnostics of the continuum and H$\beta$ emission in a prototypical Population B active galaxy
• Spectroastrometry and Reverberation Mapping of Active Galactic Nuclei. II. Measuring Geometric Distances and Black Hole Masses of Four Nearby Quasars
• The Deviation of the Broad-line Region Size Between Reverberation Mapping and Spectroastrometry
• Balmer line shifts in quasars
• Rarefied Broad-Line Regions in Active Galactic Nuclei: Anomalous Responses in Reverberation Mapping and Implications for Weak Emission-Line Quasars
• Modeling the Reverberation Response of the Broad Line Region in Active Galactic Nuclei II: Incorporating Photoionization Models
• Reverberation Mapping Data of NGC 5548 Imply a Multicomponent Broad-Line Region