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VLBI images of 49 radio supernovae in Arp 220

Lonsdale, Colin J. and Diamond, Philip J. and Thrall, Hannah and Smith, Harding E. and Lonsdale, Carol J. (2006) VLBI images of 49 radio supernovae in Arp 220. Astrophysical Journal, 647 (1). pp. 185-193. ISSN 0004-637X. doi:10.1086/505193.

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We have used a very long baseline interferometry (VLBI) array at 18 cm wavelength to image the nucleus of the luminous IR galaxy Arp 220 at ∼1 pc linear resolution, with very high sensitivity. The resulting map has an rms of 5.5 μJy beam to the -1, and careful image analysis results in 49 confirmed point sources ranging in flux density from 1.2 mJy down to ∼60 μJy. Comparison with high-sensitivity data from 12 months earlier reveals at least four new sources. The favored interpretation of these sources is that they are radio supernovae, and if all new supernovae are detectable at this sensitivity, a resulting estimate of the supernova rate in the Arp 220 system is 4 ± 2 per year. The implied star formation rate is sufficient to power the entire observed far-infrared luminosity of the galaxy. The two nuclei of Arp 220 exhibit striking similarities in their radio properties, although the western nucleus is more compact, and appears to be ∼3 times more luminous than the eastern nucleus. There are also some puzzling differences, and differential free-free absorption, synchrotron aging, and expansion losses may all be playing a role. Comparison with the nearby starburst galaxy M82 supports the hypothesis that the activity in Arp 220 is essentially a scaled-up version of that in M82.

Item Type:Article
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Lonsdale, Colin J.0000-0003-4062-4654
Lonsdale, Carol J.0000-0003-0898-406X
Additional Information:© 2006 The American Astronomical Society. Received 2006 March 6; accepted 2006 April 14. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. 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 European VLBI Network is a joint facility of European, Chinese, South African and other radio astronomy institutes funded by their national research councils. This work was partially supported by NSF grant AST-0352953 to Haystack Observatory. We thank Rob Beswick for help in compiling data on M82, and useful comments on the manuscript.
Group:Infrared Processing and Analysis Center (IPAC)
Subject Keywords:active—galaxies: individual (Arp 220)—galaxies: starburst—infrared: galaxies—radio continuum: galaxies—supernovae
Issue or Number:1
Record Number:CaltechAUTHORS:LONapj06
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Official Citation:Colin J. Lonsdale et al 2006 ApJ 647 185
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:7317
Deposited By: Lindsay Cleary
Deposited On:30 Jan 2007
Last Modified:08 Nov 2021 20:41

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