Relativistic beaming effects in the spectra of cores and hotspots in radio galaxies and quasars |
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| Authors: | C H Ishwara-Chandra D J Saikia |
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| Institution: | National Centre for Radio Astrophysics, TIFR, Post Bag 3, Ganeshkhind, Pune 411 007, India;Joint Astronomy Programme, Department of Physics, Indian Institute of Science, Bangalore 560 012, India;Raman Research Institute, Sadashiva Nagar, Bangalore 560 080, India |
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| Abstract: | We present the results of multiwavelength 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 of the quasars in our sample, whereas only ～50 per cent of the galaxies have cores detected in at least one of the wavelengths . 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, with the distributions in a matched sample of core-dominated quasars, shows that the distributions for these two classes are significantly different, and this is consistent with the expectations of the unified scheme. The difference in the spectral indices of the two hotspots on opposite sides is also significantly larger for quasars than for radio galaxies, as is expected in the unified scheme. We also investigate the relationship between the spectral index of the hotspots and the redshift or luminosity for our sample of sources. |
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| Keywords: | galaxies: active galaxies: nuclei quasars: general radio continuum: galaxies |
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