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Astron. Astrophys. 344, 402-408 (1999)

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1. Introduction

3C 119 is a typical Compact Steep Spectrum (CSS) radio source with a well defined turnover in its spectrum around 80 MHz and an overall physical extent of [FORMULA] pc. It is now generally agreed that CSS sources as a class are small because they are young objects, whose jets have not had time to extend to the larger (kiloparsec) scales usually associated with classical double-lobed radio sources (Fanti et al. 1995, for example); the most recent evidence for this point of view is provided by the proper-motion studies of Owsianik & Conway (1998) and Owsianik et al. (1999). However, it is also likely that at least some CSS sources are small due to the existence of a dense medium that confines the jet to the nuclear region and prevents it from forming larger-scale structure. Using the 45-m telescope at Nobeyama, Kato et al.(1987) and Inoue et al. (1995) measured very large rotation measures for 3C 119 (RM [FORMULA] rad/m2), and proposed that they were primarily intrinsic to the source; this suggested that 3C 119 might be among those CSS sources whose expansion is hindered by a dense medium.

The earliest Very Long Baseline Interferometry (VLBI) investigations of 3C 119 ([FORMULA], V = 20) were made independently at 1.6 GHz with the US VLBI network (Pearson et al. 1980), MERLIN (Spencer et al. 1989), and the European VLBI network (Fanti et al. 1985). The most detailed VLBI studies of the source presented so far have been done at 5 GHz by Fanti et al. (1986) and at 1.6 GHz by Nan et al. (1991). In the latter work, the high dynamic range image reveals a complex spiral-like structure in which a number of components are embedded.

We present below the results of VLBI polarimetry of 3C 119 using the Very Long Baseline Array (VLBA). Simultaneous data were obtained at three significantly different frequencies in the available 8.4-GHz band with nearly identical uv coverage. This has enabled us to determine the polarization properties of the source on milliarcsecond scales, resolve the external Faraday screen in front of the most luminous component, and reveal the geometry and intensity of the intrinsic magnetic fields of the source. This investigation has yielded useful information for our understanding of the energy transport process and interactions between the VLBI jet and its surrounding environment.

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© European Southern Observatory (ESO) 1999

Online publication: March 18, 1999