RESULTS FROM THE RADIOASTRON AGN POLARIZATION KSP: A LIMB-BRIGHTENED JET IN 3C273

The RadioAstron active galactic nuclei (AGN) polarization Key Science Project (KSP) aims at exploiting the unprecedented angular resolution provided by RadioAstron to study jet launching/collimation and magnetic-field configuration in AGN jets. The targets of our KSP are some of the most powerful blazars in the sky. I will present observations at 1.4 GHz and 22 GHz of 3C273, performed in 2014, designed to reach a maximum baseline of approximately ∼9 Earth diameters. We find that the nuclear brightness temperature estimate at 22 GHz is two orders of magnitude lower than the exceptionally high value detected in 2013 during the RadioAstron AGN survey (1.4×10^13 K, source-frame), and even one order of magnitude lower than the equipartition value. This suggests that extreme brightness temperatures are a short-lived phenomenon caused by a temporary departure from equipartition. At L-band, we observe for the first time a limb-brightened structure along the jet, complementary to the spine-brightened one detected at 5 GHz by the Strong-AGN KSP. This supposes a jet stratification, with different velocities across the axis, or a helical magnetic field wrapping the jet.

Fecha: 
13/12/2018 - 12:30
Conferenciante: 
Gabriele Bruni
Filiación: 
INAF-IAPS, Rome, Italy


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