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III Zw 2: Evolution of a Radio Galaxy in a Nutshell

Published online by Cambridge University Press:  05 March 2013

A. Brunthaler
Affiliation:
Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany. brunthal@mpifr-bonn.mpg.de
H. Falcke
Affiliation:
Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany. brunthal@mpifr-bonn.mpg.de
G. C. Bower
Affiliation:
RAL, University of California at Berkeley, 601 Campbell Hall, CA 94720, USA.
M. F. Aller
Affiliation:
University of Michigan, Astronomy Department, Ann Arbor, MI 48109-1090, USA.
H. D. Aller
Affiliation:
University of Michigan, Astronomy Department, Ann Arbor, MI 48109-1090, USA.
H. Teräsranta
Affiliation:
Metsähovi Radio Observatory, Metsähovintie, 02540 Kylmälä, Finland.
T. P. Krichbaum
Affiliation:
Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany. brunthal@mpifr-bonn.mpg.de
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Abstract

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III Zw 2 shows dramatic radio outbursts roughly every five years. Here we present the light curves and VLBA observations of the latest flare with an excellent time sampling. We have detected superluminal motion with a lower limit for the apparent expansion speed of 1.25±0.09 c at 43 GHz. Spectral and spatial evolution are closely linked and the evolution of III Zw 2 in a turnover frequency vs. linear size diagram is similar to the correlation for GPS and CSS sources. Before and after this rapid expansion we observe a period of virtually no expansion. However, at 15 GHz III Zw 2 shows a constant slow expansion (∼0.6 c). The difference is qualitatively explained by optical depth effects in an ‘inflating-balloon model’, describing the evolution of radio lobes on an ultra-compact scale. The stop-and-go behaviour could be explained by a jet interacting with a molecular cloud or the molecular torus.

Type
GPS/CSS Workshop
Copyright
Copyright © Astronomical Society of Australia 2003

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