Wide-Field Imaging and Polarimetry for the Biggest and Brightest in the 20GHz Southern Sky

We present wide-field imaging and polarimetry at 20GHz of seven of the most extended, bright (Stot >= 0.50 Jy), high-frequency selected radio sources in the southern sky with declinations < -30 deg. Accompanying the data are brief reviews of the literature for each source, The results presented here aid in the statistical completeness of the Australia Telescope 20GHz Survey's bright source sample. The data are of crucial interest for future cosmic microwave background missions as a collection of information about candidate calibrator sources. We are able to obtain data for seven of the nine sources identified by our selection criteria. We report that Pictor A is thus far the best extragalactic calibrator candidate for the Low Frequency Instrument of the Planck European Space Agency mission due to its high level of integrated polarized flux density (0.50+/-0.06 Jy) on a scale of 10 arcmin. Six of the seven sources have a clearly detected compact radio core, with either a null or less than two percent detection of polarized emission from the nucleus. Most sources with detected jets have magnetic field alignments running in a longitudinal configuration, however PKS1333-33 exhibits transverse fields and an orthogonal change in field geometry from nucleus to jets.Comment: 17 pages, 9 figures, 2 table

Evolution of structure in cold dark matter universes

We present an analysis of the clustering evolution of dark matter in four cold dark matter (CDM) cosmologies. We use a suite of high resolution, 17-million particle, N-body simulations which sample volumes large enough to give clustering statistics with unprecedented accuracy. We investigate a flat model with #OMEGA#_0 = 0.3, an open model also with #OMEGA#_0 = 0.3, and two models with #OMEGA# = 1, one with the standard CDM power spectrum and the other with the same power spectrum as the #OMEGA#_0 = 0.3 models. In all cases, the amplitude of primordial fluctuations is set so that the models reproduce the observed abundance of rich galaxy clusters by the present day. The mass two-point correlation function and power spectrum of all the simulations differ significantly from those of the observed galaxy distribution, in both shape and amplitude. Thus, for any of these models to provide an acceptable representation of reality, the distribution of galaxies must be biased relative to the mass in a non-trivial, scale-dependent, fashion. In the #OMEGA# = 1 models the required bias is always greater than unity, but in the #OMEGA#_0 = 0.3 models an ''antibias'' is required on scales smaller than #propor to#5h&quot;-&quot;1 Mpc. The mass correlation functions in the simulations are well fit by recently published analytic models. The velocity fields are remarkably similar in all the models, whether they be characterised as bulk flows, single-particle or pairwise velocity dispersions. This similarity is a direct consequence of our adopted normalisation and contradicts the common belief that the amplitude of the observed galaxy velocity fields can be used to constrain the value of #OMEGA#_0. The small-scale pairwise velocity dispersion of the dark matter is somewhat larger than recent determinations from galaxy redshift surveys, but (orig.)120 refs.SIGLEAvailable from TIB Hannover: RR 4697(1048) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman