Dynamics of line-driven disk winds in active galactic nuclei

Daniel Proga, James M. Stone, Timothy R. Kallman

Research output: Contribution to journalArticlepeer-review

568 Scopus citations

Abstract

We present the results of axisymmetric time-dependent hydrodynamic calculations of line-driven winds from accretion disks in active galactic nuclei (AGNs). We assume the disk is flat, Keplerian, geometrically thin, and optically thick, radiating according to the α-disk prescription. The central engine of the AGN is a source of both ionizing X-rays and wind-driving UV photons. To calculate the radiation force, we take into account radiation from the disk and the central engine. The gas temperature and ionization state in the wind are calculated self-consistently from the photoionization and heating rate of the central engine. We find that a disk accreting onto a 108 M black hole at the rate of 1.8 M yr-1 can launch a wind at ∼1016 cm from the central engine. The X-rays from the central object are significantly attenuated by the disk atmosphere so they cannot prevent the local disk radiation from pushing matter away from the disk. However, in the supersonic portion of the flow high above the disk, the X-rays can overionize the gas and decrease the wind terminal velocity. For a reasonable X-ray opacity, e.g., κX = 40 g-1 cm2, the disk wind can be accelerated by the central UV radiation to velocities of up to 15,000 km s-1 at a distance of ∼1017 cm from the central engine. The covering factor of the disk wind is ∼0.2. The wind is unsteady and consists of an opaque, slow vertical flow near the disk that is bounded on the polar side by a high-velocity stream. A typical column density through the fast stream is a few times 1023 cm-2 so the stream is optically thin to the UV radiation. This low column density is precisely why gas can be accelerated to high velocities. The fast stream contributes nearly 100% to the total wind mass-loss rate of 0.5 M yr-1.

Original languageEnglish (US)
Pages (from-to)686-696
Number of pages11
JournalAstrophysical Journal
Volume543
Issue number2 PART 1
DOIs
StatePublished - Nov 10 2000

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Keywords

  • Accretion, accretion disks
  • Galaxies: active
  • Hydrodynamics
  • Instabilities
  • Methods: numerical

Fingerprint Dive into the research topics of 'Dynamics of line-driven disk winds in active galactic nuclei'. Together they form a unique fingerprint.

Cite this