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Session 10 - AGN - Host Galaxies & Environment.
Display session, Monday, January 13
We present multi-frequency VLBA polarimetric observations of the Compact Steep Spectrum (CSS) quasar OQ 172 in the 6 and 18 cm bands. This object was previously known to have anomalously high Faraday rotation measures (RMs) -- in excess of 20,000 rad m^-2 in the rest frame of the source. With a resolution of 2 mas, we confirm the high RMs seen at lower resolution and further find that the high RMs are associated with the nuclear component. Only 10 mas from the nucleus the jet |RM|s fall to less than 100 rad m^-2 -- low enough to be produced entirely by the passage of the radiation through the interstellar medium of our galaxy. Such differences in the RM structure on scales of 50 parsecs rule out a cluster magnetic field Faraday screen thought to be the dominant mechanism for producing the high RM objects seen at lower redshift. We suggest that the high RMs seen in OQ 172, and perhaps in other CSS quasars as well, originate in the nuclear environment.
Program listing for Monday