Astron. Astrophys. 355, 863-872 (2000)

The radio continuum spectrum of Centaurus A's large-scale components

H. Alvarez ¹, J. Aparici ¹, J. May ¹ and P. Reich <sup>2

1</sup> Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile
² Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany

Received 27 January 1999 / Accepted 4 January 2000

Abstract

Using our own observations at 45 MHz and data found in the literature after an exhaustive search, we have attempted a comprehensive study of the integrated flux density spectrum of the Centaurus A radio galaxy and of its large scale components. The spectrum for the whole object, between 10 and 4750 MHz, can be well represented by a power law with a spectral index of , disproving the existence of a spectral break reported by other authors in the past. Between 406 and 4750 MHz we present, for the first time, the spectra of the individual Giant Outer Lobes and find that, within the errors of measurement, their spectral indices are practically equal. We show that the Giant Outer Lobes contribute with 73% of the total luminosity of the object. That the indices of the different large scale components are close or equal supports the double injection hypothesis for their origin. We discuss the spectral indices and luminosities, and we determine upper bounds for the ages of the radiating electrons. We show that Centaurus A supports the P- rather than the z- correlation.

Key words: galaxies: individual: NGC 5128 = Cen A galaxies: active radio continuum: galaxies

Send offprint requests to: H. Alvarez

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Contents

• 1. Introduction
• 2. The data
  • 2.1. The total integrated flux density at 45 MHz
  • 2.2. Integrated flux densities at other frequencies
• 3. Discussion
  • 3.1. The spectrum of the Whole Source
  • 3.2. The spectrum of the Inner Lobes
  • 3.3. The spectrum of the Giant Outer Lobes
  • 3.4. Luminosities
  • 3.5. Spectral aging
  • 3.6. P- correlation
• 4. Conclusions
• Acknowledgements
• References

© European Southern Observatory (ESO) 2000

Online publication: March 21, 2000
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