A radio and optical study of Molonglo radio sources

Abstract

We present multi-wavelength radio observations with the Very Large Array and narrow- and broad-band optical observations with the 2.5m telescope at the Las Campanas Observatory, of a well-defined sample of high-luminosity Fanaroff-Riley class II radio galaxies and quasars, selected from the Molonglo Reference Catalogue 1-Jy sample. These observations were carried out as part of a programme to investigate the effects of orientation and environment on some of the observed properties of these sources. We examine the dependence of the Liu-Pooley relationship, which shows that radio lobes with flatter radio spectra are less depolarized, on size, identification and redshift, and show that it is significantly stronger for smaller sources, with the strength of the relationship being similar for both radio galaxies and quasars. In addition to Doppler effects, there appears to be intrinsic differences between the lobes on opposite sides. We discuss the asymmetry in brightness and location of the hotspots, and present estimates of the ages and velocities from matched resolution observations at L- and C-bands. The narrow- and broad-band optical images of some of these sources were made to study their environments and correlate with the symmetry parameters. Extended emission-line region is seen in a quasar and in four of the objects, possible companion galaxies are seen close to the radio axis.

11 pages, accepted for publication in MNRAS. Complete set of radio images can be obtained from [email protected]

References in corpus (5)

• The spectra and energies of classical double radio lobes
• Giant Radio Sources
• The Molonglo Reference Catalog 1-Jy radio source survey IV. Optical spectroscopy of a complete quasar sample
• A Polarization Study of Radio Galaxies and Quasars selected from the Molonglo Complete Sample
• Relativistic beaming effects in the spectra of cores and hotspots in radio galaxies and quasars

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• On the Evolution of the Cores of Radio Sources and Their Extended Radio Emission
• Decoding the giant extragalactic radio sources
• The cluster environments of radio-loud quasars at 0.6 < z < 1.1
• The depolarisation properties of powerful extragalactic radio sources as a function of cosmic epoch
• J1432+158: the most distant giant quasar
• Powerful Radio Sources in the Southern Sky. I. Optical Identifications
• 3C254: MERLIN observations of a highly asymmetric quasar