East-West Linear Polarization Distributions of Radio Galaxies at 1418 MHz

Abstract

view Abstract Citations (19) References (72) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS East-West Linear Polarization Distributions of Radio Galaxies at 1418 MHz Sejelstad, G. A. ; Weller, K. W. Abstract We have examined the distributions along a circle of constant declination of the linearly polarized radiation at a frequency of 14t8 MHz from sizty-eight extragalactic radio sources. The effective resolution was 08. At places within many sources very high degrees of polarization (>t5 per cent), usually accompanied by a constant plane of polarization, were found. Both facts imply the existence of a highly ordered magnetic field. Often other regions within the same source also contained a uniform field, but oriented differently. Less frequently the field is well ordered over an entire component or even over the entire source. These regions of uniformity can exceed galactic dimensions ( 100 kpc). The distributions of linearly polarized and total radiation, obtained at nearly the same frequency with identical resolution, have been compared. In general, the two distributions bear little resemblance: one certainly cannot predict the distribution of linearly polarized radiation from a knowledge of the distribution of total radiation. An important exception is the class of core-halo sources. For these, most of the linearly polarized radiation, at least at decimetric wavelengths, originates in the halo. The cores have a very low degree of polarization, except possibly at short centimetric wavelengths. Because the polarization distributions in many cases are broader than the total distributions, we suggest that halos about radio sources may occur more commonly than supposed. For the identified objects we have sought distinctive polarization properties among the various optical classes. It appears that cD galaxies either have unusually low integrated degrees of polarization or atypical dependences of polarization parameters on wavelength. The other optical classes appear indistinguishable on the basis of their linear polarization properties. We have suggested that depolarization occurs largely within the sources themselves. We propose that emission and Faraday rotation occur together within the source components but that only emission occurs in the outskirts. Publication: The Astrophysical Journal Supplement Series Pub Date: June 1969 DOI: 10.1086/190186 Bibcode: 1969ApJS...18...85S full text sources ADS |