MERLIN POLARIZATION OBSERVATIONS OF COMPACT STEEP-SPECTRUM SOURCES AT5 GHZ

We present polarization observations of 28 compact steep-spectrum sour ces made with the upgraded MERLIN at 5 GHz. With an angular resolution of 60 milliarcsec and rms noise levels of about 0.1 mJy beam(-1), the total intensity images reveal new details in many of these sources. A few of the more extended lobes and jets are quite highly polarized, b ut more than half of the components are completely unpolarized. Compar ison with published data implies that this is due to Faraday depolariz ation, probably occurring in the surrounding medium with nB similar to 1 cm(-3) mu G. The high resolution of the present observations implie s that the variations in Faraday rotation, probably due to magnetic he ld tangling, occur on scales of less than about 100 pc.