FNWI --- IMAPP Department of Astrophysics
Radboud University > Faculty of Science > Department of Astrophysics

Jets and lobes

In the radio regime one often observes collimated outflows that originate in the center of a galaxy and terminate in giant lobes outside the optical galaxy itself. It has been established that these so called jets are launched by the supermassive black holes in the centers of the galaxies. These black holes are accreting their surrounding gas and part of the energy liberated in the accretion flow is injected into these collimated outflows. What causes these jets and how do they interact with their environment?

Image: F. Owen et al. NRAO/STSCI/NMIMT The somehow exceptional characteristics of these sources are their sheer linear sizes, which could extent much further than their optical counterpart, and their power in the radio band of the electromagnetic spectrum could be so high that these could be observed up to cosmological distances.

After the jets have been launched (see section on magnetohydrodynamics) they first propagate into the interstellar medium and then into the intergalactic medium for a typical time of 100 million years. Finally, they terminate in so called hot-spots, which are not always observable. These are shock regions between the jets and the intergalactic medium. The built-up jet material and/or energy carried by the jets is diffused into the radio lobes. These could be observed as diffuse and low surface brightness emission features between the hot-spots and the core of the AGN.

We are involved in the observation of jets and lobes on all scales: From the compact core of the jet up to the giant lobes. The resulting images are interpreted with the developed jet models (analytical and numerical). Besides studying the jet itself, we are also observing the interaction of the jet with his surrounding medium, for example we are trying to understand how the power liberated in the AGN is coupled to its surrounding gas. This is one key ingredient to the problem of AGN feedback. Besides the direct effects of the jet we are also studying jets and lobes as laboratories for cosmic ray production. Some of our current research focuses on the energetics and particle content of the giant lobes of the radio galaxy Centaurus A.