Anisotropy in the Distribution of Galactic Radio Polarizations

Radiation traversing the observable universe provides powerful ways to test isotropy of electromagnetic propagation. A controversial recent study claimed a signal of dipole character. We characterize a new and independent data set of 277 points under the null proposal of statistical independence of polarization orientations and angular positions. The null hypothesis is tested via maximum likelihood analysis of best fits among numerous independent types of factored distributions. We also extract single-number correlations which are parameter free, invariant under coordinate transformations, and distributed very robustly. We find that the null proposal is not supported at the level of less than 5% to less than 0.1% by several independent statistics. The data indicate an axis of correlation, on the basis of likelihood determined to be $[{\rm R.A.}=(23^{h},19^{m}) \pm (1^{h},22^{m})$, ${\rm Decl.} = 15^o\pm 20^o]$.