Brunthaler, Falcke et al. 2000: III Zw 2, first superluminal Seyfert

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

Andreas Brunthaler 1 Heino Falcke1, Geoffrey C. Bower1,2, Margo F. Aller3, Hugh D. Aller3, Harri Teräsranta4, Andrew R. Lobanov1, Thomas P. Krichbaum1, Alok R. Patnaik1

1Max-Planck-Institut für Radioastronomie, Auf den Hüugel 69, D-53121 Bonn, Germany (
2Current address: NRAO, P.O. Box O, Socorro, NM 87801-0387
3Astronomy Department, University of Michigan, Ann Arbor, MI 48109-1090
4Metsähovi Radio Research Station, Metsahovintie, SF-02540 Kylmäalä, Finland

Astronomy & Astrophysics Letters, Vol. 357, L45-L48 (2000)


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 1.25 +/- 0.09 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.

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