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Compact OH megamaser and probable quasar activity in the galaxy Arp 220

Nature volume 370, pages 117–120 (1994)Cite this article

Abstract

ARP 220 is the prototype far-infrared ultraluminous galaxy, and the origin of its luminosity—a burst of massive star formation or a quasar obscured by a layer of dense gas and dust—has been the subject of much debate1,2. It also contains the prototypical OH megamaser3—an extremely luminous version of masers (microwave lasers) commonly found in our own galaxy. It has been thought that the dense gas in the inner few hundred parsecs of megamaser galaxies acts as a low-gain masing screen, pumped by the far-infrared radiation, which amplifies background continuum emission from the nuclear regions4–6. Here we show, using new very-long-baseline interferometry observations, that the OH line peak in Arp 220 originates in a structure ⩽1 pc across, position-ally aligned with a weak continuum feature, and that most of the emission originates on scales of ⩽ 10 pc. These results imply that the maser is physically 10–100 times smaller than previously thought5,6, strongly suggesting that much of the far-infrared radia-tion from Arp 220 arises in a very small region, possibly a dense molecular torus, surrounding a quasar nucleus.

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Authors and Affiliations

  1. Haystack Observatory, Massachusetts Institute of Technology, Off Route 40, Westford, Massachusetts, 01886, USA

    Colin J. Lonsdale

  2. National Radio Astronomy Observatory, PO Box 0, Socorro, New Mexico, 87801, USA

    Philip J. Diamond

  3. Center for Astrophysics and Space Sciences and Department of Physics, University of California, San Diego, La Jolla, California, 92093-0111, USA

    Harding E. Smith

  4. Infrared Processing and Analysis Center and Jet Propulsion Laboratory, California Institute of Technology 100-22, Pasadena, California, 01125, USA

    Harding E. Smith & Carol J. Lonsdale

Authors
  1. Colin J. Lonsdale
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  4. Carol J. Lonsdale
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Lonsdale, C., Diamond, P., Smith, H. et al. Compact OH megamaser and probable quasar activity in the galaxy Arp 220. Nature 370, 117–120 (1994). https://doi.org/10.1038/370117a0

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