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Title: The effects of irradiation on cloud evolution in active galactic nuclei

We report on the first phase of a study of cloud irradiation. We study irradiation by means of numerical, two-dimensional, time-dependent radiation hydrodynamic simulations of a strongly irradiated cloud. We adopt a very simple treatment of the opacity, neglect photoionization and gravity, and focus instead on assessing the role of the type and magnitude of the opacity on the cloud evolution. Our main result is that even relatively dense clouds that are radiatively heated (i.e., with significant absorption opacity) do not move as a whole; instead, they undergo very rapid and major evolution in shape, size, and physical properties. In particular, the cloud and its remnants become optically thin in less than 1 sound-crossing time and before they can travel a significant distance (a few initial-cloud radii). We also find that a cloud can be accelerated as a whole under quite extreme conditions, i.e., the opacity must be dominated by scattering. However, the acceleration due to the radiation force is relatively small, and unless the cloud is optically thin, it quickly undergoes changes in size and shape. We discuss implications for the modeling and interpretation of the broad-line regions of active galactic nuclei.
Authors:
;  [1] ; ;  [2] ;  [3]
  1. Department of Astronomy, University of Las Vegas, Las Vegas, NV 89119 (United States)
  2. Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States)
  3. Canadian Institute for Theoretical Astrophysics. Toronto, ON M5S3H4 (Canada)
Publication Date:
OSTI Identifier:
22348345
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 780; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABSORPTION; ACCELERATION; EVOLUTION; GALAXY NUCLEI; GRAVITATION; HYDRODYNAMICS; INSTABILITY; IRRADIATION; PHOTOIONIZATION; RADIANT HEAT TRANSFER; SCATTERING; SIMULATION; SOUND WAVES; TIME DEPENDENCE; TWO-DIMENSIONAL CALCULATIONS