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

Lonsdale, Colin J. and Diamond, Philip J. and Smith, Harding E. and Lonsdale, Carol J. (1994) Compact OH megamaser and probable quasar activity in the galaxy Arp 220. Nature, 370 (6485). pp. 117-120. ISSN 0028-0836.

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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 debate. It also contains the prototypical OH megamaser—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 regions. 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 thought, 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.

Item Type:Article
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URLURL TypeDescription ReadCube access
Lonsdale, Colin J.0000-0003-4062-4654
Lonsdale, Carol J.0000-0003-0898-406X
Additional Information:© 1994 Nature Publishing Group. Received 14 December 1993; accepted 24 May 1994. We thank M. Titus and L. Sims for technical assistance, and R. Barvainis, J. Krolik, D. van Buren, M. Reid and J. Moran for discussions and advice. This work was supported at Haystack Observatory by the US National Science Foundation. This work was carried out in part by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA.
Group:Infrared Processing and Analysis Center (IPAC)
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Issue or Number:6485
Record Number:CaltechAUTHORS:20150609-100414067
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:58106
Deposited By: Tony Diaz
Deposited On:09 Jun 2015 17:29
Last Modified:30 Sep 2020 17:39

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