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Spectral Ages of CSOs and CSS Sources

Published online by Cambridge University Press:  05 March 2013

Matteo Murgia
Matteo Murgia*
Affiliation:
Istituto di Radioastronomia del CNR, Via Gobetti 101, I−40129 Bologna, Italy. [email protected]
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Abstract

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This paper deals with the spectral ageing study of a representative sample of compact symmetric objects (CSOs) and compact steep spectrum (CSS) sources. Observations reveal a distinctive high-frequency steepening of the radio spectra of many of these sources. The existence of such a spectral feature is expected or may be naturally interpreted in terms of radiative ageing of synchrotron emitting electrons. The small angular size of CSS sources makes it relatively easy to measure their integrated spectra over a wide frequency range for a conspicuous number of objects. For those sources whose emission is dominated by the mini-lobes, the integrated spectra can be used to constrain the source age. Assuming equipartition magnetic fields, the spectral ages we found are in the range from 102 to 105 yr. Multifrequency VLBA observations allow us to study the spectral properties of two CSOs: B1323+321 and B1943+546. The case of B1943+546 is particularly interesting since for this source a kinematic age has been derived from the proper motion of the hot spots. We found that spectral and kinematic ages agree within a factor of 2. The overall results presented here confirm that the CSOs and CSS sources are indeed young objects. Finally, we show some examples of compact sources characterised by an extraordinary steep and curved spectrum. It is plausible that these are relic sources in which the injection of fresh electrons has ceased for a significant fraction of their lifetime. These observations may indicate either the presence of intermittent activity or a class of short-living objects.

Throughout this paper we adopt H0 = 100 h km s−1 Mpc−1 and q0 = 0.5.

Keywords

radio continuum: galaxiesgalaxies: evolution
Type
GPS/CSS Workshop
Information
Publications of the Astronomical Society of Australia , Volume 20 , Issue 1 , 2003 , pp. 19 - 24
Copyright
Copyright © Astronomical Society of Australia 2003

References

Carvalho, J. C. 1985, MNRAS, 215, 463 CrossRefGoogle Scholar
Dallacasa, D., Fanti, C., Fanti, R., Schilizzi, R. T., & Spencer, R. E. 1995, A&A, 295, 27 Google Scholar
Fanaroff, B. L., & Riley, J. M. 1974, MNRAS, 167, 31 CrossRefGoogle Scholar
Fanti, C., Fanti, R., Dallacasa, D., Schilizzi, R. T., Spencer, R. E., & Stanghellini, C. 1995, A&A, 302, 317 Google Scholar
Fanti, C., Pozzi, F., Dallacasa, D., Fanti, R., Gregorini, L., Stanghellini, C., & Vigotti, M. 2001, A&A, 369, 380 Google Scholar
Jaffe, W. J., & Perola, G. C. 1974, A&A, 26, 423 Google Scholar
Kardashev, N. S. 1962, SvA, 6, 317 Google Scholar
Kellermann, K. I. 1964, ApJ, 140, 969 CrossRefGoogle Scholar
Murgia, M., Fanti, C., Fanti, R., Gregorini, L., Klein, U., Mack, K.-H., & Vigotti, M. 1999, A&A, 345, 769 Google Scholar
O'Dea, C. P., & Baum, S. A. 1997, ApJ, 113, 148 CrossRefGoogle Scholar
Owsianik, I., & Conway, J. E. 1998, A&A, 337, 69 Google Scholar
Owsianik, I., Conway, J. E., & Polatidis, A. G. 1998, A&A, 336, 37L Google Scholar
Pacholczyk, A. G. 1970, Radio Astrophysics (San Francisco: Freeman & Co.)Google Scholar
Peacock, J. A., & Wall, J. V. 1981, MNRAS, 194, 19 Google Scholar
Phillips, T. J., & Mutel, R. L. 1982, A&A, 106, 21 Google Scholar
Polatidis, A. G., & Conway, J. E. 2003, PASA, 20, in pressCrossRefGoogle Scholar
Polatidis, A. G., Wilkinson, P. N., Xu, W., Readhead, A. C. S., Pearson, T. J., Taylor, G. B., & Vermeulen, R. C. 1995, ApJS, 98, 1 CrossRefGoogle Scholar
Reynolds, C., & Begelman, M. 1997, ApJ, 487, L135 CrossRefGoogle Scholar
Snellen, I. A. G., Schilizzi, R. T., Miley, G. K., Bremer, M. N., Röttgering, H. J. A., & van Langevelde, H. J. 1999, NewAR, 43, 675 CrossRefGoogle Scholar
Siemiginowska, A., Bechtold, J., Aldcroft, T. L., Elvis, M., Harris, D. E., & Dobrzycki, A. 2002, ApJ, 570, 543 CrossRefGoogle Scholar
van Breugel, W. J. M., Miley, G. K., & Heckman, T. A. 1984, AJ, 89, 5 CrossRefGoogle Scholar
Zappacosta, L. 2000, Diploma Thesis, University of Bologna Google Scholar