Intergalactic Magnetic Fields and Faraday Rotation of Extragalactic Radio Sources

Abstract

Abstract This paper reexamines our earlier statistical analyses of rotation measures RM and redshifts z of extragalactic radio sources. Absolute magnitudes of RM of 97 sources at high galactic latitudes, |b|35°, are shown to increase with z. Correlation coefficients r between RM and z cos θ are calculated for various presumed directions of the intergalactic magnetic field, where θ denotes the angle between a source and the field direction. We have obtained a correlation coefficient of r=0.60 among 51 sources of z≥0.5 and |b| >35°. The z-dependence of RM is interpreted by a uniform intergalactic magnetic field of 2.7×10−9 G running in the direction of l=100°, b=15° in space up to z=2.