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Astron. Astrophys. 337, 69-79 (1998)

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First detection of hotspot advance in a Compact Symmetric Object

Evidence for a class of very young extragalactic radio sources

I. Owsianik 1 and J.E. Conway 2

1 Toru Centre for Astronomy, Radio Astronomy Department, ul.Gagarina 11, PL-87-100 Toru, Poland (iza@astro.uni.torun.pl)
2 Onsala Space Observatory, S-439 92 Onsala, Sweden (jconway@oso.chalmers.se)

Received 2 December 1997 / Accepted 21 April 1998


We present the results of multi-epoch global VLBI observations of the Compact Symmetric Object (CSO), 0710+439 at 5 GHz. Analysis of data spread over 13 years shows strong evidence for an increase in the separation of the outer components at a rate of [FORMULA]. Dividing the overall size of 86.8 [FORMULA]pc by this separation rate implies an estimated kinematic age of only [FORMULA] yrs. After taking into account possible temporal variations in hotspot advance speeds due to cloud collisions or hydrodynamic instabilities we argue that the upper limit to the age of 0710+439 is most likely within a factor of 2 of this estimate and certainly within a factor of 10 (i.e. [FORMULA] yrs). This result therefore strongly supports the idea that Compact Symmetric Objects are very young radio-loud sources. Furthermore the large radiative efficiency we calculate for 0710+439 is consistent with strong negative luminosity evolution as CSOs grow in size and with them evolving into classical double sources.

Key words: radio continuum: galaxies – galaxies: active – galaxies: compact – galaxies: evolution – galaxies: individual: 0710+439

Send offprint requests to: I. Owsianik

© European Southern Observatory (ESO) 1998

Online publication: August 6, 1998