A preferred orientation of extragalactic double radio sources

The distribution of the main axes of double radio sources is used to test isotropy of that part of the universe which is accessible to radio investigations. Data for 274 double and/or extended sources have been taken from the literature to compute the fit to several simple models of global orientation by means of a ²-test. The best fit has been found on a 3%-significance level for the preferred orientation along a right-handed helix with pitch angle 82° in the direction =95°, =–38° (165°,b=20°). This preferential alignment of radio sources is assumed to be caused by a largescale magnetic field.