Rotation Measure Distribution in Compact Steep-steep Spectrum Sources

Abstract

We have used radio polarization data at different frequencies to obtain the rotation measure, RM, the source rest frame rotation measure, RM(1+z)² and the spectral index, α in a sample of Compact Steepspectrum Sources (CSSs). The CSS quasar sub-sample has RM(1+z)² median values of ~-15.01 and 14.13 for the jet and counter-jet sides respectively, while corresponding values for galaxies are ~ -3.23 and 5.86. Spectral index asymmetry was also found with median spectral index values of ~1.11 and 1.50 for the jet and counter-jet sides of the quasar sub-sample, and the galaxy sub-sample has corresponding values of ~0.95 and 1.23; while there is no significant correlation between rotation measure and spectral index. The asymmetries observed could be due to a combination of both intrinsic and orientation effects.

Keyword: Rotation Measure, Compact Steep-spectrum Sources, Galaxies, Quasar and Spectral Index.