Polarization Of Radio Sources Research Articles

The Linear Polarization of Radio Sources at 6 cm Wavelength

Linear po1a.rization measurements at 6 cm wavelength with the Parkes 210 ft telescope are given for 706 sources. Comparison of polarization parameters and flux densities with other published data is made. For the variable sources it is found that changes in polarized flux and position angle can accompany changes in intensity.

The Linear Polarization of Radio Sources Between 11 and 20 cm Wavelength. II. Polarization and Related Properties of Extragalactic Sources

The polarization properties of quasars, radio galaxies, and unidentified objects at 11 and 20 cm wavelength are discussed and compared with other source characteristics. For some quasars, scintillation and spectral data are in accord with current ideas that the sources comprise a small component radiating only at high frequencies and a larger component with a radiation spectrum similar to radio galaxies. The polarization is associated with this second component. For radio galaxies, the lower polarization of scintillators and a decrease of luminosity with increasing polarization suggest that sources of high brightness have low polarization. In spectral and polarization characteristics, the unidentified sources are similar to radio galaxies. Source evolution is discussed; the results suggest that quasars and radio galaxies evolve separately rather than represent different stages of a single evolutionary sequence.

Linear Polarization of Radio Sources at 2.07-CENTIMETER Wavelength

view Abstract Citations (21) References (28) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Linear Polarization of Radio Sources at 2.07-centimeter Wavelength Hobbs, R. W. ; Hollinger, J. P. Abstract Measurements of the linearly polarized 2.07-cm-wavelength radiation from twenty-nine radio sources were made, using the 140-foot paraboloidal reflector at the National Radio Astronomy Observatory. In addition, the linear polarization was measured for several regions of five of these sources: Taurus A, Centaurus A, 3C 398, Cygnus A, and Cassiopeia A. Sixteen of the sources are extragalactic, including six quasi-stellar radio sources and five variable radio sources Publication: The Astrophysical Journal Pub Date: November 1968 DOI: 10.1086/149772 Bibcode: 1968ApJ...154..423H full text sources ADS | data products NED (23) SIMBAD (1)

A Stochastic Theory for the Wavelength Dependence of Linear Polarization of Radio Sources

A Stochastic Theory for the Wavelength Dependence of Linear Polarization of Radio Sources

Observations of the Linear Polarization of Radio Sources at 6 cm Wavelength

The polarizations of 45 sources have been measured at 6 cm wavelength and have been compared with values obtained at longer wavelengths. The resulting wavelength dependence has been studied in relation to the spectra of the sources. For the quasi. stellar objects in particular, polarization features at short wave� lengths are associated with the young components of the source which radiate at high frequency. However, it is not possible to distinguish between radio galaxies and quasi-stellar objects solely on the basis of polarization data.

Polarization of Radio Sources. I. Homogeneous Source of Arbitrary Optical Thickness

view Abstract Citations (39) References (5) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Polarization of Radio Sources. I. Homogeneous Source of Arbitrary Optical Thickness Pacholczyk, A. G. ; Swihart, T. L. Abstract Solutions of the equation of transfer are obtained, and the degree of polarization is derived for a homogeneous source in which polarized emission, polarized absorption, and Faraday rotation aie included. Only 6ptically thin cases have been considered in previous works, and the present equations show how the polarization is influenced by absorption Polarization measurements may help to determine whether synchrotron self-absorption, thermal absorption, or another process is responsible for the curvature in the spectra of certain radio sources at the low frequencies in which absorption is thought to be important. Publication: The Astrophysical Journal Pub Date: November 1967 DOI: 10.1086/149364 Bibcode: 1967ApJ...150..647P full text sources ADS | Related Materials (2) Part 2: 1970ApJ...161..415P Part 3: 1971ApJ...170..405P

A Stochastic Theory for the Wavelength Dependence of Linear Polarization of Radio Sources.

The following model is proposed: The source contains n elementary radiators or cells of equal power output which have perfect linear polarization independent of frequency. Some cells m have identical polarization angles, while the remaining n-m cells have polarization angles which are independent random variables with a uniform probability density function over the range 0 to 2ir. Between each cell and the observer is a medium which produces Faraday rotation of the polarization angles. The Faraday rotations are independent Gaussian random variables with a standard deviation of R rad/m2. The fractional polarization is the expected value of the sum of the polarization vectors divided by n, and is given by the formula u(N) = [(2n)-'+m(m- 1)n-0 exp(-R2N4)j1, where N is the wavelength in meters. The model fits the observations of many radio galaxies and quasi-stellar sources including 3C33, MSH 23-64, 3C196, and Her A; but it fails to fit the observations of Cyg A and Tan A. The source Cyg A has an increase in fractional polarization with wavelength near 1 cm, but the model can give only constant or decreasing fractional polarization with wavelength. Extensions of the model which could describe Cyg A and Tan A seem feasible. The average rotation measure of the source (a measurable quantity) is independent of the fractional polarization in the present theory. Burn and Sciama (Monthly Not~ces Roy. Astron. Soc. 133, 5,1966) have described a theory based on a Fourier transform relation between the fractional polarization and a function which distributes the radiated power with Faraday depth. (At a certain Faraday depth, the number of rotations to the observer is constant.) The Burn and Sciama theory requires that the average polarization angle of each Faraday depth is identical, but no such assumption is required in the present theory.

Linear Polarization of Radio Sources at a Wavelength of 21.3 cm

THE Cambridge One-Mile radio telescope1 has recently been used to make high resolution observations of a number of radio sources (refs. 2 and 3, and Macdonald, G. H., in preparation). Observations of the Crab Nebula, Cygnus A and the sources 3C 47, 103, 332, 338 and 4C (7 29.41 have been repeated with the receiving horns of the telescope set at 90° to their original direction, thus providing maps of these sources at two perpendicular polarizations; although these maps do not allow the unique distribution of polarization across the sources to be obtained, the results are nevertheless of some interest.

Measurements of the Linear Polarization of Radio Sources at 18-cm Wavelength.

view Abstract Citations References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Measurements of the Linear Polarization of Radio Sources at 18-cm Wavelength. Morris, D. ; Radhakrishnan, V. ; Seielstad, G. A. Abstract Measurements have been made with the Caltech radio interferometer to determine the linear polarization of the t8-cm radiation from a number of small-diameter radio sources. By combining the resulting values with those obtained previously at t0.6 cm (Seielstad, G. A., Morris, D., and Radhakrishnan, V., Astrophys. J., in press) and 2t.2 cm (Seielstad, G. A., and Wilson, R. W., Nature 198, 274, t963) the magnitude and sign of the Faraday rotation of the plane of polarization can be obtained. In addition, the dependence of fractional polarization on frequency is similarly obtained. Taken together with the corresponding values obtained by Gardner and Whiteoak (Nature 197, tt62, t963) information is now available for 25 sources. The observed polarization characteristics of the sources are discussed as a function of their galactic coordinates and their physical properties in an attempt to locate the magneto-ionic medium causing the Faraday rotation, and to determine the process responsible for their depolarization curves. The work was supported by the U. S. Office of Naval Research under contract Nonr 220(19). Publication: The Astronomical Journal Pub Date: October 1963 DOI: 10.1086/109013 Bibcode: 1963AJ.....68..542M full text sources ADS |

Linear Polarization of 21-cm Wave-length Radiation from Radio Sources

A SYSTEMATIC search for linear polarization of radio sources has been carried out at this Observatory at three frequencies and several antenna separations. A detailed discussion of the results obtained awaits further analysis and will be published elsewhere. However, the measurements made during September 1962 at a wave-length of 21 cm have been completely analysed. The preliminary results have been reported previously1.

Polarization of Radio Sources and Faraday Rotation Effects in the Galaxy

Polarization of Radio Sources and Faraday Rotation Effects in the Galaxy

The Polarization of Radio Sources.

The Polarization of Radio Sources.