Radio polarimetry of compact steep spectrum sources at sub-arcsecond resolution

Aims. We report new Very Large Array (VLA) polarimetric observations of compact steep-spectrum (CSS) sources at 8.4, 15, and 23 GHz. Methods. Using multi-frequency VLA observations we have derived sub-arcsecond resolution images of the total intensity, polarisation, and rotation measure (RM) distributions. Results. We present multi-frequency VLA polarisation observations of CSS sources. About half of the sources are point-like even at the resolution of similar to 0.1 x 0.1 arcsec. The remaining sources have double or triple structure. Low values for the percentage of polarised emission in CSS sources is confirmed. On the average, quasars are more polarised than galaxies. A wide range of RM values have been measured. There are clear indications of very large RMs up to approximate to 5585 radm(-2). CSS galaxies are characterized by RM values that are larger than CSS quasars. The majority of the objects show very large values of RM. Conclusions. The available data on sub-arcsecond-scale rest-frame RM estimates for CSS sources show that these have a wide range of values extending up to similar to 36 000 radm(-2). RM estimates indicate an overall density of the magneto-ionic medium larger than classical radio sources.