The spectral-curvature parameter: an alternative tool for the analysis of synchrotron spectra

B. W. Sohn; U. Klein; K. -H. Mack

doi:10.1051/0004-6361:20030435

paper

The spectral-curvature parameter: an alternative tool for the analysis of synchrotron spectra

arXiv:astro-ph/0304155 · doi:10.1051/0004-6361:20030435

Abstract

The so-called Spectral Curvature Parameter(SCP), when plotted versus the high-frequency spectral index ( $a l p h a_{hi g h}$ ) of synchrotron sources, provides crucial parameters on the continuum spectrum of synchrotron radiation without the more complex modeling of spectral ageing scenarios. An important merit of the SCP- $a l p ha$ diagram is the enhanced reliability of extracting multiple injection spectra, $a l p h a_{inj}$ . Different from the colour-colour diagram, tracks of different $a l p h a_{inj}$ s, especially when the synchrotron particles are young, exhibit less overlap and less smearing in the SCP- $a l p ha$ diagram. Three giant radio galaxies(GRGs) and a sample of Compact steep spectrum(CSS) souces are presented. GRGs exhibit asymmetries of their injection spectral indices $a l p h a_{inj}$ in the SCP- $a l p h a_{hi g h}$ diagram. The obtained $a l p h a_{inj}$ s and the trends in the sources are cross-checked with the literature and show remarkable confidence. Besides the spectral steepening, spectral flattening is prominent in the radio lobes. The spectral flattening is a clue to efficient re-acceleration processes in the lobes. It implies interaction with the surrounding intergalactic or intra-cluster medium is an important characteristic of GRGs. In the SW lobe of DA240, there is a clear sign of CI and KP/JP bifurcation at the source extremity. This indicates a highly relativistic energy transportation from the core or in situ acceleration in this typical FR I lobe. Our analysis proves, if exists, KP spectra imply the existence of strong $B_{sy n c}$ field with $B_{sy n c} > B_{C M B}$ . In the CSS sources, our result confirms the CI model and $B_{sy n c} >> B_{C M B}$ . The synchrotron self-absorption is significant in the CSS sample.

to be published in A&A

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Signatures in a Giant Radio Galaxy of a Cosmological Shock Wave at Intersecting Filaments of Galaxies

The spectral-curvature parameter: an alternative tool for the analysis of synchrotron spectra

Abstract

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