Vol. 583
In section 13. Astronomical instrumentation

RadioAstron space VLBI imaging of polarized radio emission in the high-redshift quasar 0642+449 at 1.6 GHz

The long-awaited era of space VLBI observations on scales greater than the Earth's diameter began with the 2011 launch of the 10-meter Space Radio Telescope, as an element of the RadioAstron network. Operating between 326 MHz and 22 GHz, this antenna combines with the ground-based VLBI network to produce projected baselines from 1.6 to nearly 6 terrestrial diameters (up to several hundred Mlambda). This important paper reports the observational procedure and first results of the polarization studies carried out during the science verification stage of the mission that took place in March 2014 on the flat spectrum radio quasar 0642+449 at a resolution of 1 mas. The core, which contains 98% of the flux, is resolved into two components separated by about 2 mas and a weak jet whose base is separated from the core by 4 mas. All components are polarized. The peak of the polarized jet emission is not observed along its axis but with a longitudinal field orientation while the field in the core is transverse to the jet. The authors discuss the details of the polarization measurements and also the limits on the source brightness temperature, taking into consideration light of beaming and resolution problems.