The First IRAM/PdBI Polarimetric Millimeter Survey of Active Galactic Nuclei. I. Global Properties of the Sample

We have studied the linear polarization of 86 active galactic nuclei (AGN) in the observed frequency range 80-267 GHz (3.7-1.1mm in wavelength), corresponding to rest-frame frequencies 82-738 GHz, with the IRAM Plateau de Bure Interferometer (PdBI). The large number of measurements, 441, makes our analysis the largest polarimetric AGN survey in this frequency range to date. We extracted polarization parameters via earth rotation polarimetry with unprecedented median precisions of ~0.1% in polarization fractions and ~1.2 degrees in polarization angles. For 73 of 86 sources we detect polarization at least once. The degrees of polarization are as high as ~19%, with the median over all sources being ~4%. Source fluxes and polarizations are typically highly variable, with fractional variabilities up to ~60%. We find that BLLac sources have on average the highest level of polarization. There appears to be no correlation between degree of polarization and redshift, indicating that there has been no substantial change of polarization properties since z~2.4. Our polarization and spectral index distributions are in good agreement with results found from various samples observed at cm/radio wavelengths; thus our frequency range is likely tracing the signature of synchrotron radiation without noticeable contributions from other emission mechanisms. The "millimeter-break" located at frequencies >1 THz appears to be not detectable in the frequency range covered by our survey.Comment: 19 pages, 9 figures, 2 long tables (p. 12-19). Accepted by A&A

High-frequency polarization properties of southern Kuhr sources

We have carried out observations at 18.5 GHz with the Australia Telescope Compact Array (ATCA) of 250 out of the 258 Southern extragalactic sources in the complete 5 GHz 1 Jy sample by K\"uhr et al. (1981). In this paper we focus on the polarization properties of this sample, while other properties will be addressed in a future paper. In our analysis we subdivide the sample into flat and steep spectrum sources following Stickel et al. (1994) classification, where spectral indices were measured between 2.7 and 5 GHz. The polarized flux has been measured with a S/N > 5 for 170 sources (114 flat-spectrum and 56 steep-spectrum) and upper limits have been set for additional 27 sources (12 flat-spectrum and 15 steep-spectrum). The median polarization degree at 18.5 GHz for the flat-spectrum sub-sample is \Pi_{18.5}\simeq 2.7%, about a factor of 2 higher than at 1.4 GHz (\Pi_{1.4}\simeq 1.4%, based on NVSS data). For flat-spectrum sources we find a weak correlation between \Pi_{18.5} and the high frequency (5--18.5 GHz) spectral index. No evidences of significant correlations of the polarization degree with other source properties are found. The median value of \Pi_{18.5} for the steep spectrum sources is \simeq 4.8%, but our sample might be biased against extended sources. We find indications of a correlation between \Pi_{18.5} and both the low frequency (1.4--5 GHz) and the high frequency (5--18.5 GHz) spectral indices. An important application of this work is the possibility to estimate the contamination of CMB polarization maps by extragalactic radio sources. Our results indicate that such contamination is within the range of estimates given by Mesa et al. (2002).Comment: 11 pages, 8 Postscripts figures, 6 tables, accepted for publication on A&A, minor typos correcte

A search for linear polarization in the active galactic nucleus 3C 84 at 239 and 348 GHz

We report a search for linear polarization in the active galactic nucleus (AGN) 3C 84 (NGC 1275) at observed frequencies of 239 GHz and 348 GHz, corresponding to rest-frame frequencies of 243 GHz and 354 GHz. We collected polarization data with the IRAM Plateau de Bure Interferometer via Earth rotation polarimetry. We do not detect linear polarization. Our analysis finds 3-sigma upper limits on the degree of polarization of 0.5% and 1.9% at 239 GHz and 348 GHz, respectively. We regard the influence of Faraday conversion as marginal, leading to expected circular polarizations <0.3%. Assuming depolarization by a local Faraday screen, we constrain the rotation measure, as well as the fluctuations therein, to be 10^6 rad/m^2. From this we estimate line-of-sight magnetic field strengths of >100 microG. Given the physical dimensions of 3C 84 and its observed structure, the Faraday screen appears to show prominent small-scale structure, with \DeltaRM > 10^6 rad/m^2 on projected spatial scales <1 pc.Comment: 7 pages, 4 figures. Accepted by MNRA

Space Applications of the Geant4 Simulation Toolkit

The space radiation environment is highly variable and dynamic. With the increasing number and complexity of space missions, the detailed analysis of the effects of that environment often requires the use of advanced Monte Carlo radiation transport tools. In this presentation, various space-oriented developments and applications based on the Geant4 particle transport toolkit are described

GEANT4 : a simulation toolkit

Abstract Geant4 is a toolkit for simulating the passage of particles through matter. It includes a complete range of functionality including tracking, geometry, physics models and hits. The physics processes offered cover a comprehensive range, including electromagnetic, hadronic and optical processes, a large set of long-lived particles, materials and elements, over a wide energy range starting, in some cases, from 250 eV and extending in others to the TeV energy range. It has been designed and constructed to expose the physics models utilised, to handle complex geometries, and to enable its easy adaptation for optimal use in different sets of applications. The toolkit is the result of a worldwide collaboration of physicists and software engineers. It has been created exploiting software engineering and object-oriented technology and implemented in the C++ programming language. It has been used in applications in particle physics, nuclear physics, accelerator design, space engineering and medical physics. PACS: 07.05.Tp; 13; 2

GEANT4--a simulation toolkikt

Geant4 is a toolkit for simulating the passage of particles through matter. It includes a complete range of functionality including tracking, geometry, physics models and hits. The physics processes offered cover a comprehensive range, including electromagnetic, hadronic and optical processes, a large set of long-lived particles, materials and elements, over a wide energy range starting, in some cases, from 250 eV and extending in others to the TeV energy range. It has been designed and constructed to expose the physics models utilised, to handle complex geometries, and to enable its easy adaptation for optimal use in different sets of applications. The toolkit is the result of a worldwide collaboration of physicists and software engineers. It has been created exploiting software engineering and object-oriented technology and implemented in the C++ programming language. It has been used in applications in particle physics, nuclear physics, accelerator design, space engineering and medical physics

A Millimetre/Submillimetre Polarization Survey of Compact Flat-Spectrum Radio Sources

‘The definitive version is available at www3.interscience.wiley.com '.Peer reviewe

Submillimetre Polarimetry of Blazars

Original paper can be found at: http://www.astrosociety.org/pubs/cs/070-112.html--Copyright Astronomical Society of the PacificWe report on preliminary results from the first monitoring campaign of the submillimetre polarization of a sample of Blazars. The observations have been carried out with the James Clerk Maxwell Telescope between 1991 and 1994