Line-driven disk winds in active galactic nuclei: The critical importance of ionization and radiative transfer

Journal Article · Tue Jul 01 04:00:00 EDT 2014 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/789/1/19· OSTI ID:22356516

Higginbottom, Nick; Knigge, Christian; Matthews, James H. ^[1]; Proga, Daniel ^[2]; Long, Knox S. ^[3]

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1. School of Physics and Astronomy, University of Southampton, Highfield, Southampton, SO17 1BJ (United Kingdom)
2. Department of Physics and Astronomy, University of Nevada, Las Vegas, 4505 South Maryland Parkway, Las Vegas, NV 89154-4002 (United States)
3. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

Accretion disk winds are thought to produce many of the characteristic features seen in the spectra of active galactic nuclei (AGNs) and quasi-stellar objects (QSOs). These outflows also represent a natural form of feedback between the central supermassive black hole and its host galaxy. The mechanism for driving this mass loss remains unknown, although radiation pressure mediated by spectral lines is a leading candidate. Here, we calculate the ionization state of, and emergent spectra for, the hydrodynamic simulation of a line-driven disk wind previously presented by Proga and Kallman. To achieve this, we carry out a comprehensive Monte Carlo simulation of the radiative transfer through, and energy exchange within, the predicted outflow. We find that the wind is much more ionized than originally estimated. This is in part because it is much more difficult to shield any wind regions effectively when the outflow itself is allowed to reprocess and redirect ionizing photons. As a result, the calculated spectrum that would be observed from this particular outflow solution would not contain the ultraviolet spectral lines that are observed in many AGN/QSOs. Furthermore, the wind is so highly ionized that line driving would not actually be efficient. This does not necessarily mean that line-driven winds are not viable. However, our work does illustrate that in order to arrive at a self-consistent model of line-driven disk winds in AGN/QSO, it will be critical to include a more detailed treatment of radiative transfer and ionization in the next generation of hydrodynamic simulations.

• OSTI ID: 22356516
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 789; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ACCRETION DISKS
BLACK HOLES
COMPUTERIZED SIMULATION
FEEDBACK
GALAXIES
GALAXY NUCLEI
MASS TRANSFER
MATHEMATICAL SOLUTIONS
MONTE CARLO METHOD
QUASARS
RADIANT HEAT TRANSFER
SPECTRA
STELLAR WINDS