Colloq Abstract - Savolainen
October 21
11am Mountain
Tuomas Savolainen
Zooming in where the jets are born - RadioAstron space-VLBI observations of nearby radio galaxies
Abstract
Understanding the mechanisms for launching, accelerating, and collimating the magnetized jets of plasma from accreting black holes remains 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 especially in the field of general relativistic magnetohydrodynamic simulations.
High-resolution radio imaging of (sub-)parsec-scale structures in the jets 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 results from both ground- and space-based very long baseline interferometry observations of jets. I will mainly concentrate on the results from the RadioAstron space-VLBI imaging of nearby radio galaxies. We have successfully obtained high-fidelity, near-perigee RadioAstron images of the jets in 3C84 and M87. Fringe detections up to 7.6 Earth diameter baseline lengths on 3C84 provide information on the structures down to scales of 27 microarcseconds at 22 GHz. The 22 GHz image of 3C84 reveals the jet collimation region: the jet is strongly edge-brightened, it starts out with a wide opening angle and collimates very quickly into a cylindrical shape. The M87 L-band space-VLBI image reveals a rich structure inside the jet, including twisted, apparently helicalfilaments. These may be similar to the filaments previously seen at the arcsecond scale, but just much closer to the central engine.
