Origin of Warm High-Velocity Dense Gas in ULIRGs

Abstract

Possible origins of the molecular absorption discovered in some ULIRGs are investigated, based on a 3-D hydrodynamic model of star-forming interstellar gas in a galactic central region. The blue-shifted, warm ($\sim 200-300$ K), dense ($>10^6$ cm${}^{-3}$) molecular gas suggested by CO absorption in IRAS 08752+3915 could be caused by the innermost region of the inhomogeneous inter-stellar medium (ISM) around a supermassive black hole. The infrequent observations of the dense gas with absorption in ULIRGs and Seyfert 2 galaxies could simply suggest that the high-density regions occupy only a very small volume fraction of the obscuring material. This is naturally expected if the inhomogeneous structure of the ISM is caused by non-linear development of instabilities. The model predicts a turbulent velocity field in the obscuring material, therefore blue- and red-shifted gases should be observable with nearly the same probability for the large enough statistical samples.

14 pages, 6 figures. Publications of Astronomical Society of Japan in press

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Cited by in corpus (4)

• Infrared Spectroscopy of CO Ro-vibrational Absorption Lines toward the Obscured AGN IRAS 08572+3915
• The 3-5 micron Spectrum of NGC 1068 at High Angular Resolution: Distribution of Emission and Absorption Features across the Nuclear Continuum Source
• Systematic Study of the Inner Structure of Molecular Tori in Nearby U/LIRGs using Velocity Decomposition of CO Rovibrational Absorption Lines
• Study of the Inner Structure of the Molecular Torus in IRAS 08572+3915 NW with Velocity Decomposition of CO Rovibrational Absorption Lines