Wednesday Colloquium


"Modeling radio emission from G2 cloud bow shock"

Aleksander Sądowski (CfA, Harvard University)

The giant molecular cloud of gas called 'G2' is currently approaching the supermassive black hole in the Galactic center. It is moving through the accretion flow with a supersonic velocity and therefore a bow shock forms ahead of it. I will discuss the radio synchrotron emission that is expected to arise in the bow shock and report on most recent observations.


"The power of jets - the radio view"

Heino Falcke (Radboud Universiteit Nijmegen, The Netherlands)

Jets are an integral part of most accreting system, particularly in black hole system of all masses. In the deep gravitational wells of black holes, matter falls towards the event horizon producing a hot, magnetized plasma producing bright radiation. Magnetic fields are wound up and produce powerful relativistic outflows, which leave the system along the rotation axis of the black hole. The overall kinetic and magnetic power released in jets can be an appreciable fraction of the overall energy produced in the accretion process. The highly magnetized plasma and relativistic speeds seem to provide ideal conditions for accelerating relativistic particles, which leads to synchrotron and inverse Compton emission ranging from radio to gamma rays. Hence, jets are inherently broad-band sources as well as candidate sources for ultra-high energy cosmic rays. Radio telescopes are particularly suited to pick out and study jets on all scales, ranging form the largest scales, probed, e.g. by the new LOFAR telescope, down to the event horizon, probed by very long baseline interferometry. The talk summarizes some of our basic understanding of radio jets and presents some recent results obtained with LOFAR and other telescopes.

The lecture will be heald (as an exception) at 3:15 pm.