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

TL;DR

This study uses multi-frequency VLA polarimetric observations to analyze the polarization and rotation measure distributions of Compact Steep-Spectrum sources at sub-arcsecond resolution, revealing large RMs and differences between quasars and galaxies.

Contribution

It provides high-resolution polarization and RM measurements of CSS sources, highlighting the range of RMs and the differences between quasars and galaxies, which was not previously well-characterized.

Findings

CSS sources exhibit low polarization percentages.

Quasars are more polarized than galaxies.

Large rotation measures up to 36,000 rad m**(-2) are observed.

Abstract

Aims - We report new Very Large Array polarimetric observations of Compact Steep-Spectrum (CSS) sources at 8.4, 15, and 23GHz. Methods - Using multi-frequency VLA observations we have derived sub-arcsecond resolution images of the total intensity, polarisation, and rotation measure (RM) distributions. Results heading - We present multi-frequency VLA polarisation observations of CSS sources. About half of the sources are point-like even at the resolution of about 0.1x0.1 arcseconds. 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 5\,585 rad m**(-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 about 36,000 rad m**(-2). RM estimates indicate an overall density of the magneto-ionic medium larger than classical radio sources.