The Structure and Dynamics of An Active Galactic Nucleus Torus: CO Line Predictions for ALMA from Three-dimensional Hydrodynamical Simulations with X-ray-driven Chemistry

J.P. Perez Beaupuits, K. Wada, M. Spaans

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Abstract

Several attempts have been made to model the mass distribution and dynamical evolution of the circumnuclear gas in active galactic nuclei (AGNs). However, chemical evolution is not included in detail in three-dimensional (3D) hydrodynamic simulations. The X-ray radiation from the AGN can drive the gas chemistry and affect the thermodynamics, as well as the excitation of the interstellar medium. Therefore, we estimate the effects (on chemical abundances and excitation) of X-ray irradiation by the AGN for atomic and molecular gas in a 3D hydrodynamic model of an AGN torus.We obtain the abundances of various species from an X-ray chemical model. A 3D radiative transfer code estimates the level populations, which result in line intensity maps. Predictions for the CO J = 1 -> 0 to J = 9 -> 8 lines indicate that mid-J CO lines are excellent probes of density and dynamics in the central (less than or similar to 60 pc) region of the AGN in contrast to the low-J CO lines. Analysis of the X-CO/alpha conversion factors shows that only the higher J CO lines can be used for gas mass determination in AGN tori. The [C II] 158 mu m emission traces mostly the hot (T-k > 1000 K) central region of the AGN torus. The [C II] 158 mu m line will be useful for ALMA observations of high-redshift (z greater than or similar to 1) AGNs. The spatial scales (>= 0.25 pc) probed with our simulations match the size of the structures that ALMA will resolve in nearby (

Original languageEnglish
Article number48
Number of pages18
JournalAstrophysical Journal
Volume730
Issue number1
DOIs
Publication statusPublished - 20-Mar-2011

Keywords

  • galaxies: evolution
  • galaxies: ISM
  • methods: numerical
  • ULTRALUMINOUS INFRARED GALAXIES
  • REDSHIFT SUBMILLIMETER GALAXIES
  • SUPERMASSIVE BLACK-HOLES
  • NEARBY SEYFERT-GALAXIES
  • PHOTON-DOMINATED REGION
  • MOLECULAR GAS
  • CARBON-MONOXIDE
  • STAR-FORMATION
  • ROTATIONAL-EXCITATION
  • INTERSTELLAR-MEDIUM

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