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E. Momjian (NAIC, Arecibo Observatory), J. D. Romney, C. L. Carilli (NRAO), T. H. Troland (U. Kentucky)
We present phase-referenced VLBI results on the OH 18 cm megamaser emission from the Ultra-Luminous Infrared Galaxy (ULIRG), IRAS 17208-0014. The observations were carried out at 1599 MHz using the High Sensitivity Array (HSA: Very Long Baseline Array + the phased Very Large Array + the Green Bank Telescope). The observations reveal both compact and diffuse OH megamaser emission in IRAS 17208-0014. The OH emission in this ULIRG has an extent of 170 x 110 pc, and is mostly localized in two regions separated by 80 mas (61 pc). The structure and dynamics of the maser emission seem to be consistent with a clumpy, rotating, ring-like geometry, with the two dominant maser regions marking the tangential points of the proposed rotating-ring distribution. Assuming Keplerian motion, the enclosed dynamical mass and the mass density within a radius of 30.5 pc, are about {2 \times 107~M{\odot}}, and 171~M{\odot}~{\rm pc}-3, respectively. The OH megamaser results do not indicate the presence of a dominant supermassive black hole in this advanced merger system, which is consistent with previous radio continuum, IR, and optical observations.
The Arecibo Observatory is part of the National Astronomy and Ionosphere Center, which is operated by Cornell University under a cooperative agreement with the National Science Foundation. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.