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Register a new userA 98% spectroscopically complete sample of the most powerful equatorial radio sources at 408 MHz
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P. N. Best
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A new sample of very powerful radio galaxies is defined from the Molonglo Reference Catalogue, according to the criteria S (408 MHz) > 5 Jy, -30 < Dec < 10 degrees, |b| > 10 degrees. The sample is selected to have similar properties to the northern 3CR revised sample, and to be visible to a combination of existing northern telescopes such as the Very Large Array radio interferometer and large southern hemisphere telescope facilities. The sample contains 178 sources, of which spectroscopic redshifts are available in the literature for 128. For the remaining 50 sources, new radio imaging, optical imaging and spectroscopic observations are presented to identify the host galaxies and determine their redshifts. With these new observations the total sample is 100% optically identified and redshifts are available for 174 (98%) of the sources. The sample consists of one starburst galaxy, one Seyfert galaxy, 127 radio galaxies and 49 quasars. Basic properties of the sample, such as the distributions of the quasar and radio galaxy populations in redshift and their locations on the radio power versus linear size (P-D) diagram, show no significant differences from the revised 3CR sample. The equatorial location and the high spectroscopic completeness of this sample make it a valuable resource for detailed studies of the nature and environments of these important objects with the new generation of southern hemisphere telescopes.
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A new sample of very powerful radio sources, defined from the Molonglo Reference Catalogue, was recently compiled by Best, Rottgering and Lehnert (1999). These authors provided redshifts for 174 of the 178 objects in the sample, making the sample 98% spectroscopically complete. Here, redshifts for three of the remaining galaxies are presented, confirming the optical identifications and raising the spectroscopic completeness of the sample to 99.5%; only 1059-010 (3C249) is currently without redshift.
We present a new 408 MHz survey (B3.1) carried out with the Croce del Nord radiotelescope in Bologna. The survey coordinates limits are $-2^circ 00^prime$ to $+2^circ 15^prime$ in Dec. and 21h to 24h, 00h to 17h in R.A., equivalent to 0.388 sr. The B3.1 is complete to 0.15 Jy but many sources down to 0.1 Jy are included. Our aim was to select a new and complete sample of Ultra Steep Spectrum (USS) radio sources, as they proved to be good candidates to find high-z radiogalaxies and their surrounding protoclusters. The observations and the reduction procedure are described and the observational errors are discussed. A cross-identification with the NVSS survey was performed to obtain the spectral index $alpha_{408}^{1400}$ and radio size of the sources. We found no evidence of a change of the spectral index distribution as radio flux decreases. The B3.1 USS sample contains 185 sources down to 0.1 Jy and it is about one order of magnitude deeper in flux with respect to the 4C USS sample. For 146 B3.1 USS sources no optical counterpart was found on the POSS-I sky survey. A cross-correlation with the FIRST survey gave maps for a subset of 50 USS sources, and their optical ID search was also made on the POSS-II, resulting in 39 empty fields
We present high sensitivity polarimetric observations in 6 bands covering the 5.5-38 GHz range of a complete sample of 53 compact extragalactic radio sources brighter than 200 mJy at 20 GHz. The observations, carried out with the Australia Telescope Compact Array (ATCA), achieved a 91% detection rate (at 5 sigma). Within this frequency range the spectra of about 95% of sources are well fitted by double power laws, both in total intensity and in polarisation, but the spectral shapes are generally different in the two cases. Most sources were classified as either steep- or peaked-spectrum but less than 50% have the same classification in total and in polarised intensity. No significant trends of the polarisation degree with flux density or with frequency were found. The mean variability index in total intensity of steep-spectrum sources increases with frequency for a 4-5 year lag, while no significant trend shows up for the other sources and for the 8 year lag. In polarisation, the variability index, that could be computed only for the 8 year lag, is substantially higher than in total intensity and has no significant frequency dependence.
A new catalogue of extended radio sources has been prepared based on arcminute-resolution 1420 MHz images from the Canadian Galactic Plane Survey (CGPS). The new catalogue provides both 1420 MHz and 408 MHz flux density measurements on sources found near the Galactic plane in the second quadrant of our Galaxy. In addition cross-identifications are made with other major radio catalogues and information is provided to facilitate the recovery of CGPS image data associated with each catalogued source. Numerous new radio sources are identified and the catalogue provides a comprehensive summary of both newly discovered and previously known HII regions and supernova remnants in the outer Galaxy. The catalogue should be of use both for synoptic studies of Galactic structure and for placing higher resolution observations, at radio and other wavelengths, in context.
We use three samples (3CRR, 6CE and 6C*) to investigate the radio luminosity function (RLF) for the `most powerful low-frequency selected radio sources. We find that the data are well fitted by a model with a constant co-moving space density at high redshift as well as by one with a declining co-moving space density above some particular redshift. This behaviour is very similar to that inferred for steep-spectrum radio quasars by Willott et al (1998) in line with the expectations of Unified Schemes. We conclude that there is as yet no evidence for a `redshift cut-off in the co-moving space densities of powerful classical double radio sources, and rule out a cut-off at z < 2.5.
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