VLBI polarimetry of the high rotation measure source 3C 119 at 8.4 GHz

We have mapped the distribution of the rotation measure of the CSS source 3C 119 on milliarcsecond scales using VLBA observations obtained at three widely-separated frequencies in the available 8.4-GHz band. The resulting images at frequencies 8.16, 8.52, and 8.86 GHz demonstrate that the material associated with the large integrated rotation measure of the source is concentrated near the brightest jet component C. There is a large, smooth gradient of the rotation measure in this component of 2300 rad/m2/mas, with the largest rotation measure at the leading edge. This supports the idea that C is associated with a collision between the VLBI jet and a dense intergalactic cloud. The magnetic field in C is aligned with the flow into C from the northeast, and swings through ∼ 45◦ so that it remains aligned with the inferred flow toward the emission further down the jet, nearly directly to the south.