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Polarization Survey (polarization + survey)

Distribution by Scientific Domains
Physics and Astronomy100%

Selected Abstracts

Identifying Compact Symmetric Objects from the VLBA Imaging and Polarization Survey

ASTRONOMISCHE NACHRICHTEN, Issue 2-3 2009
S.E. Tremblay
Abstract Compact Symmetric Objects (CSOs) are small (less than 1 kpc) radio sources which have symmetric double lobes or jets. The dominant theory for the small size of these objects is that they are young radio sources which could grow into larger radio galaxies, but the currently small population of known CSOs makes it difficult to definitively determine whether or not this is the case. While a greater number of Gigahertz peaked sources can be identified by sifting through spectral surveys, this yields none of the dynamics of the sources, and also brings Quasars into the sample, which although interesting are peaked around 1 Gigahertz for very different reasons. We have used the 5 GHz VLBA Imaging and Polarization Survey (VIPS) to identify 103 CSO candidates morphologically, and are following up on these sources with multifrequency VLBA observations to confirm CSO identifications and to study their dynamics. The identification of candidates from within the survey will be discussed, as well as preliminary results from the follow-up observations (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Toru, 6-cm polarimetry of the MilkyWay

ASTRONOMISCHE NACHRICHTEN, Issue 5-6 2006
S. Ry
Abstract We present first results of a radio continuum and polarization survey of the Milky Way at 4.7 GHz carried out with the 32-m radio telescope in Toru,. The survey is much less affected by depolarization effects than previous measurements at lower frequencies. This enables the study of magnetic field structure and its interrelations with particular features in the interstellar medium to much larger distances from the Sun. Our preliminary total power map shows a good association of radio features with galactic star-forming regions while the polarization data reveal an increasing coherence of magnetic fields away from the Galaxy's mid-plane. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Biases in the polarization position angles in the NRAO-VLA sky survey point source catalogue

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2008
R. A. Battye
ABSTRACT We have examined the statistics of the polarization position angles determined for point sources in the NRAO-VLA Sky Survey (NVSS), and find that there is a statistically significant bias towards angles which are multiples of 45°. The formal probability that the polarization angles are drawn from a uniform distribution is exponentially small. When the sample of those NVSS sources with polarizations detected with a signal-to-noise ratio ,3 is split either around the median polarized flux density or the median fractional polarization, the effect appears to be stronger for the more highly polarized sources. Regions containing strong sources and regions at low-Galactic latitudes are not responsible for the non-uniform distribution of position angles. We identify clean bias as the probable cause of the dominant effect, coupled with small multiplicative and additive offsets on each of the Stokes parameters. Our findings have implications for the extraction of science, such as information concerning galactic magnetic fields, from large-scale polarization surveys. [source]