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

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 <sup>2

1</sup> 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

Abstract

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 . Dividing the overall size of 86.8 pc by this separation rate implies an estimated kinematic age of only 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. 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

SIMBAD Objects

Contents

• 1. Introduction
• 2. General source properties
  • 2.1. Optical properties
  • 2.2. Radio properties
• 3. Observations and imaging
  • 3.1. Observations
  • 3.2. Data reduction
  • 3.3. Source structure
• 4. Multi-epoch intercomparison
  • 4.1. Procedure
  • 4.2. Component position and flux variations
  • 4.3. Bulk motion or internal structure changes?
  • 4.4. Motions relative to the core
• 5. Discussion
  • 5.1. Hotspot advance speeds and source age
  • 5.2. Implications for CSO models
• Acknowledgements
• Appendix
  • A.1. Reliability of features in CLEAN maps
  • A.2. Estimating modelfitting component position errors
  • A.3. Biasing due to cross self-calibration
• References

© European Southern Observatory (ESO) 1998

Online publication: August 6, 1998
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