Relativistic beaming effects in the spectra of cores and hotspots in radio galaxies and quasars

Abstract

We present the results of multi-wavelength observations of cores and hotspots at L, C, X and U bands with the Very Large Array, of a matched sample of radio galaxies and quasars selected from the Molonglo Reference Catalogue. We use these observations to determine the spectra of cores and hotspots, and test the unified scheme for radio galaxies and quasars. Radio cores have been detected at all wavelengths in all the quasars in our sample, while only $\sim$ 50% of the galaxies have detected cores in at least one wavelength. The degree of core prominence in this sample is consistent with the unified scheme for radio galaxies and quasars. A comparison of the distributions of the two-point spectral index of the cores in our sample of lobe-dominated quasars (LDQs) with a matched sample of core-dominated quasars (CDQs) shows that the distributions for these two classes are significantly different, consistent with the expectations of the unified scheme. The difference in the spectral indices of the two hotspots on opposite sides are also significantly larger for quasars than radio galaxies, as expected in the unified scheme. We also investigate the relationship between the spectral index of the hotspots and redshift or luminosity for our sample of sources.

10 pages, 9 figures, to appear in MNRAS

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• Asymmetry of jets, lobe size and spectral index in radio galaxies and quasars
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