Photoionization Modelling of the Giant Broad-Line Region in NGC 3998

Abstract

Prior high angular resolution spectroscopic observations of the Low-ionization nuclear emission-line region (Liner) in NGC 3998 obtained with the Space Telescope Imaging Spectrograph (STIS) aboard the Hubble Space Telescope (HST) revealed a rich UV-visible spectrum consisting of broad permitted and broad forbidden emission lines. The photoionization code XSTAR is employed together with reddening-insensitive emission line diagnostics to constrain a dynamical model for the broad-line region (BLR) in NGC 3998. The BLR is modelled as a large H${}^{+}$ region $\sim$ 7 pc in radius consisting of dust-free, low density $\sim$ 10${}^4$ cm${}^{-3}$, low metallicity $\sim$ 0.01 $Z/Z_{\odot }$ gas. Modelling the shape of the broad H$\alpha$ emission line significantly discriminates between two independent measures of the black hole mass, favouring the estimate of de Francesco et al. (2006). Interpreting the broad H$\alpha$ emission line in terms of a steady-state spherically symmetric inflow leads to a mass inflow rate of 1.4 $\times$ 10${}^{-2}$ M${}_{\odot }$/yr, well within the present uncertainty of calculations that attempt to explain the observed X-ray emission in terms of an advection-dominated accretion flow (ADAF). Collectively, the model provides an explanation for the shape of the H$\alpha$ emission line, the relative intensities and luminosities for the H Balmer, [O III], and potentially several of the broad UV emission lines, as well as refining the initial conditions needed for future modelling of the ADAF.

arXiv commentAccepted for publication in MNRAS, 10 pages, 8 figures

References in corpus (39)

• Advection-Dominated Accretion: A Self-Similar Solution
• The Host Galaxies and Classification of Active Galactic Nuclei
• Central Masses and Broad-Line Region Sizes of Active Galactic Nuclei. II. A Homogeneous Analysis of a Large Reverberation-Mapping Database
• The SBF Survey of Galaxy Distances. IV. SBF Magnitudes, Colors, and Distances
• Determining Central Black Hole Masses in Distant Active Galaxies and Quasars. II. Improved Optical and UV Scaling Relationships
• A Search for "Dwarf" Seyfert Nuclei. III. Spectroscopic Parameters and Properties of the Host Galaxies
• A fundamental plane of black hole activity
• The Low-Luminosity End of the Radius-Luminosity Relationship for Active Galactic Nuclei
• The Relationship Between Luminosity and Broad-Line Region Size in Active Galactic Nuclei
• A Search for "Dwarf" Seyfert Nuclei. IV. Nuclei with Broad H-alpha Emission
• Chaotic cold accretion onto black holes
• Modeling reverberation mapping data II: dynamical modeling of the Lick AGN Monitoring Project 2008 dataset
• What the Optical Recombination Lines Can Tell Us About the Broad Line Regions of Active Galactic Nuclei
• The Nuclear Reddening Curve for Active Galactic Nuclei and the Shape of the Infra-Red to X-Ray Spectral Energy Distribution
• Three-dimensional Relativistic MHD Simulations of Active Galactic Nuclei Jets: Magnetic Kink Instability and Fanaroff-Riley Dichotomy
• Spectral Models for Low-luminosity Active Galactic Nuclei in LINERs: The Role of Advection-dominated Accretion and Jets
• Low-Luminosity Active Galactic Nuclei: Are They UV-Faint and Radio Loud?
• Chaotic cold accretion on to black holes in rotating atmospheres
• Modeling reverberation mapping data I: improved geometric and dynamical models and comparison with cross-correlation results
• Locally Optimally-Emitting Clouds and the Variable Broad Emission Line Spectrum of NGC 5548
• On The Nature of Low Luminosity Narrow Line AGN
• Locally Optimally-emitting Clouds and the Narrow Emission Lines in Seyfert Galaxies
• Spectral Energy Distributions of Weak Active Galactic Nuclei Associated With Low-Ionization Nuclear Emission Regions
• A Revised Calibration of the Virial Mass Estimator for Black Holes in Active Galaxies Based on Single-epoch H$\beta$ Spectra
• Testing Radiatively-Inefficient Accretion Flow Theory: an XMM-Newton Observation of NGC 3998
• The case for cases B and C: intrinsic hydrogen line ratios of the broad-line region of active galactic nuclei, reddenings, and accretion disc sizes
• A Stellar Dynamical Mass Measurement of the Black Hole in NGC 3998 from Keck Adaptive Optics Observations
• Constraints on the Broad Line Region Properties and Extinction in Local Seyferts
• Interpreting the Ionization Sequence in AGN Emission-Line Spectra
• On the Origin of Ultraviolet Emission and the Accretion Model of Low-luminosity AGNs
• Study of LINER sources with broad H(alpha) emission. Spectral energy distribution and multiwavelength correlations
• Measuring supermassive black holes with gas kinematics: the active S0 galaxy NGC 3998
• Variability and spectral energy distributions of low-luminosity active galactic nuclei: a simultaneous X-ray/UV look with Swift
• The HST view of the broad line region in low luminosity AGN
• The location of the dust causing internal reddening of active galactic nuclei
• Aperture Effects on Spectroscopic Galaxy Activity Classification
• A rare example of low surface-brightness radio lobes in a gas-rich early-type galaxy: the story of NGC 3998
• The size of BLRs of low luminous Active Galactic Nuclei
• Photoionization Modeling of the Low Luminosity Seyfert 1 Nucleus in NGC 3516

Cited by in corpus (7)

• Shaken Snow Globes: Kinematic Tracers of the Multiphase Condensation Cascade in Massive Galaxies, Groups, and Clusters
• Appreciating mergers for understanding the non-linear $M_{\mathrm{bh}}$-$M_{\ast ,\mathrm{spheroid}}$ and $M_{\mathrm{bh}}$-$M_{\ast ,\mathrm{galaxy}}$ relations, updated herein, and the implications for the (reduced) role of AGN feedback
• Reading the tea leaves in the $M_{\mathrm{bh}}$-$M_{\ast ,\mathrm{sph}}$ and $M_{\mathrm{bh}}$-$R_{\mathrm{e},\mathrm{sph}}$ diagrams: dry and gaseous mergers with remnant angular momentum
• The LOFAR view of NGC 3998, a sputtering AGN
• The long-term broad-line responsivity in MKN 110
• Inflowing Gas in the Central Parsec of M81
• The CaFe Project: Optical FeII and Near-Infrared Ca II triplet emission in active galaxies. II. The driver(s) of the Ca II and Fe II and its potential use as a chemical clock