Margrethe Wold: Active galaxies: supermassive black holes and variability

In the last few years, we have seen significant progress in the understanding of active galactic nuclei (AGN). From being peculiar objects in the Universe that were catalogued and classified for several decades, we are now at the stage where we believe we understand the basic mechanisms of AGN, namely that of accretion of matter onto a supermassive black hole. Moreover, the community has come to realize that the AGN phenomenon is an integral part of galaxy formation and that black hole activity in a galaxy has important consequences for e.g. starformation. I will review some of the recent progress in the field, and describe work that we are doing to determine black hole masses and variability properties of AGN, both which are important for understanding the role of AGN activity in galaxy formation and the physics of the accretion process itself.