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Astron. Astrophys. 357, L45-L48 (2000)


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Letter to the Editor

III Zw 2, the first superluminal jet in a Seyfert galaxy

A. Brunthaler 1, H. Falcke 1, G.C. Bower 2, M.F. Aller 3, H.D. Aller 3, H. Teräsranta 4, A.P. Lobanov 1, T.P. Krichbaum 1 and A.R. Patnaik 1

1 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
2 National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801-0387, USA
3 University of Michigan, Astronomy Department, Ann Arbor, MI 48109-1090, USA
4 Metsähovi Radio Observatory, Metsahovintie, 02540 Kylmälä, Finland

Received 3 January 2000 / Accepted 11 April 2000

Abstract

So far all relativistically boosted jets with superluminal motion have only been detected in typical radio galaxies with early type host galaxies. We have now discovered superluminal motion in the Seyfert I galaxy III Zw 2, classified as a spiral. Superluminal motion was first inferred from the spectral evolution of the source and then confirmed by VLBI observations. The lower limit for the apparent expansion speed is [FORMULA] c. The fact that the spectral and spatial evolution are closely linked demonstrates that we are dealing with real physical expansion. Prior to this rapid expansion we have seen a period of virtually no expansion with an expansion speed less than 0.04 c. Since III Zw 2 is also part of a sample of so called radio-intermediate quasars (RIQ), it confirms earlier predictions of superluminal motion for this source, based on the argument that RIQs could be relativistically boosted jets in radio-weak quasars and Seyfert galaxies.

Key words: galaxies: active – galaxies: individual: III Zw 2 – galaxies: jets – galaxies: Seyfert

Send offprint requests to: brunthal@mpifr-bonn.mpg.de

© European Southern Observatory (ESO) 2000

Online publication: June 5, 2000

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