|Submitter:||Tuomas Savolainen (MPIfR)|
|Description:|| Understanding the mechanisms for launching, accelerating, and collimating the magnetized jets of plasma from accreting black holes is one of the central questions in relativistic astrophysics. |
During the past decade significant progress has been made in the theoretical description of jet formation, and detailed models for magnetohydrodynamic acceleration and collimation now exist. High-resolution radio imaging of (sub-)parsec-scale structures in the jets, especially in polarization, is one of the very few ways to derive observational constraints for the physical conditions in the jets in or close to their acceleration and collimation site, and thus place constraints on the theory.
In this talk I will discuss the recent observational results from the VLBA regarding the jet structure, collimation, and acceleration of the flow. As these questions are also intimately related to the magnetic field strength and topology in the jet, I will also discuss the role of new high-dynamic-range, multi-frequency, polarimetric VLBI observations as a probe of the jet magnetic-field.