Non-LTE models and theoretical spectra of accretion disks in active galactic nuclei. III. Integrated spectra for hydrogen-helium disks

Ivan - Hubeny, Eric Agol, Omer Blaes, Julian H. Krolik

Research output: Contribution to journalArticle

98 Citations (Scopus)

Abstract

We have constructed a grid of non-LTE disk models for a wide range of values of black hole mass and mass accretion rate, for several values of the viscosity parameter α, and for two extreme values of the black hole spin: the maximum-rotation Kerr black hole, and the Schwarzschild (nonrotating) black hole. Our procedure calculates self-consistently the vertical structure of all disk annuli together with the radiation field, without any approximations imposed on the optical thickness of the disk, and without any ad hoc approximations to the behavior of the radiation intensity. The total spectrum of a disk is computed by summing the spectra of the individual annuli, taking into account the general relativistic transfer function. The grid covers nine values of the black hole mass between M = 1/8 × 109 and 32 × 109 M with a twofold increase of mass for each subsequent value; and eleven values of the mass accretion rate, each a power of 2 times 1 M yr-1. The highest value of the accretion rate corresponds to the total luminosity L/LEdd ≈ 0.3. We show the vertical structure of individual annuli within the set of accretion disk models, along with their local emergent flux, and discuss the internal physical self-consistency of the models. We then present the full disk-integrated spectra and discuss a number of observationally interesting properties of the models, such as optical/ultraviolet colors, the behavior of the hydrogen Lyman limit region, polarization, and the number of ionizing photons. Our calculations are far from definitive in terms of the input physics, but generally we find that our models exhibit rather red optical/UV colors. Flux discontinuities in the region of the hydrogen Lyman limit are only present in cool, low-luminosity models, while hotter models exhibit blueshifted changes in spectral slope.

Original languageEnglish (US)
Pages (from-to)710-728
Number of pages19
JournalAstrophysical Journal
Volume533
Issue number2 PART 1
StatePublished - Apr 20 2000
Externally publishedYes

Fingerprint

active galactic nuclei
accretion disks
helium
accretion
hydrogen
annuli
grids
luminosity
color
approximation
transfer function
transfer functions
radiation distribution
optical thickness
radiant flux density
discontinuity
physics
viscosity
polarization
slopes

Keywords

  • Accretion, accretion disks
  • Galaxies: active
  • Galaxies: nuclei

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

Non-LTE models and theoretical spectra of accretion disks in active galactic nuclei. III. Integrated spectra for hydrogen-helium disks. / Hubeny, Ivan -; Agol, Eric; Blaes, Omer; Krolik, Julian H.

In: Astrophysical Journal, Vol. 533, No. 2 PART 1, 20.04.2000, p. 710-728.

Research output: Contribution to journalArticle

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AU - Hubeny, Ivan -

AU - Agol, Eric

AU - Blaes, Omer

AU - Krolik, Julian H.

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N2 - We have constructed a grid of non-LTE disk models for a wide range of values of black hole mass and mass accretion rate, for several values of the viscosity parameter α, and for two extreme values of the black hole spin: the maximum-rotation Kerr black hole, and the Schwarzschild (nonrotating) black hole. Our procedure calculates self-consistently the vertical structure of all disk annuli together with the radiation field, without any approximations imposed on the optical thickness of the disk, and without any ad hoc approximations to the behavior of the radiation intensity. The total spectrum of a disk is computed by summing the spectra of the individual annuli, taking into account the general relativistic transfer function. The grid covers nine values of the black hole mass between M = 1/8 × 109 and 32 × 109 M⊙ with a twofold increase of mass for each subsequent value; and eleven values of the mass accretion rate, each a power of 2 times 1 M⊙ yr-1. The highest value of the accretion rate corresponds to the total luminosity L/LEdd ≈ 0.3. We show the vertical structure of individual annuli within the set of accretion disk models, along with their local emergent flux, and discuss the internal physical self-consistency of the models. We then present the full disk-integrated spectra and discuss a number of observationally interesting properties of the models, such as optical/ultraviolet colors, the behavior of the hydrogen Lyman limit region, polarization, and the number of ionizing photons. Our calculations are far from definitive in terms of the input physics, but generally we find that our models exhibit rather red optical/UV colors. Flux discontinuities in the region of the hydrogen Lyman limit are only present in cool, low-luminosity models, while hotter models exhibit blueshifted changes in spectral slope.

AB - We have constructed a grid of non-LTE disk models for a wide range of values of black hole mass and mass accretion rate, for several values of the viscosity parameter α, and for two extreme values of the black hole spin: the maximum-rotation Kerr black hole, and the Schwarzschild (nonrotating) black hole. Our procedure calculates self-consistently the vertical structure of all disk annuli together with the radiation field, without any approximations imposed on the optical thickness of the disk, and without any ad hoc approximations to the behavior of the radiation intensity. The total spectrum of a disk is computed by summing the spectra of the individual annuli, taking into account the general relativistic transfer function. The grid covers nine values of the black hole mass between M = 1/8 × 109 and 32 × 109 M⊙ with a twofold increase of mass for each subsequent value; and eleven values of the mass accretion rate, each a power of 2 times 1 M⊙ yr-1. The highest value of the accretion rate corresponds to the total luminosity L/LEdd ≈ 0.3. We show the vertical structure of individual annuli within the set of accretion disk models, along with their local emergent flux, and discuss the internal physical self-consistency of the models. We then present the full disk-integrated spectra and discuss a number of observationally interesting properties of the models, such as optical/ultraviolet colors, the behavior of the hydrogen Lyman limit region, polarization, and the number of ionizing photons. Our calculations are far from definitive in terms of the input physics, but generally we find that our models exhibit rather red optical/UV colors. Flux discontinuities in the region of the hydrogen Lyman limit are only present in cool, low-luminosity models, while hotter models exhibit blueshifted changes in spectral slope.

KW - Accretion, accretion disks

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KW - Galaxies: nuclei

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