SCP- α diagram analysis of CSS sources

Details SCP- α diagram analysis of CSS sources SCP- α diagram analysis of CSS sources

Jun 2002

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002evn..conf..145s&link_type=abstract

6th European VLBI Network Symposium on New Developments in VLBI Science and Technology, held in Bonn, June 25th-28th 2002, proce

Astronomy and Astrophysics

Astronomy

1

Scientific paper

We present Spectral Curvature Parameter (SCP)--spectral index (α) diagrams of 44 Compact Steep Spectrum (CSS) sources. SCP quantifies any variations of the initial power law typical of synchrotron spectra. Murgia et al. (1999) who have analyzed the integrated flux densities of a sample of CSS sources in a profound synchrotron ageing study show that these sources have moderate spectral steepening, i.e. a difference of Δ α ˜0.5 between low- and high-frequency spectral indices, which is predicted by the continuous injection model (CI). We have used this sample to test the SCP procedures which provide an alternative method for a quick analysis of synchrotron spectra. The most important results are:
- All sources are best fit with the CI model. This confirms the results of Murgia et al. (1999).
- A clear difference between sources with strong Beq > 103 μ G and weak Beq < 5 cdot 102 μ G magnetic field is seen.
- A similar correlation is found for the dependence of the projected linear sizes. More compact sources have higher SCP values, i.e. show low-frequency flattening.
- There is a marginal difference between lobe- and core-dominated sources. The SCP values of the latter tend to be higher.
- There is no correlation with the redshifts of the sources. This implies that the intrinsic magnetic fields dominate by far over the magnetic field equivalent of the cosmic microwave background.
The results demonstrate that the SCP provides crucial parameters on the continuum spectrum of synchrotron radiation without the more complex modeling.
The authors acknowledges partial support from the EC ICN RadioNET (Contract No. HPRI-CT-1999-40003).

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