The co-evolution of supermassive black holes and galaxies

One of the most important challenges facing modern cosmology concerns the formation and evolution of galaxies. In the last few years, the astronomical community has come to realize that supermassive black holes weighing up to 100 million solar masses may play a crucial role in galaxy formation. Almost every galaxy in the local Universe harbours a supermassive black hole at its center. The phase in a galaxy's evolution during which the black hole is active is called the quasar phase. During this phase, ga s in the nuclear regions is accreted onto the black hole via a hot accretion disk. While the galaxy is a quasar, its black hole grows in mass, and the luminosity produced by the accretion process can become high enough to completely outshine the light fro m all the stars in the underlying galaxy. Massive galaxies with massive central black holes are thought to have formed through the merger of smaller, gas-rich disk galaxies. During a galaxy collision, gas flows into the nuclear regions, thus feeding the growing black hole and also giving rise to intense star formation at the center of the galaxy. In the local Universe, tight empirical relations exist between black hole mass and global galaxy properties, such as the bulge mass and stellar velocity dispe rsion. The black hole and the galaxy bulge must therefore have evolved in close relationship with each other, implying that black holes constitute an integral part of galaxy formation. The interaction between star formation, black hole growth and quasar-r elated outflows and strong winds will regulate the black hole mass and leave an imprint on the galaxy bulge. In this project, we will study the relationship between black hole mass and global galaxy properties by observing galaxies with low-mass bulges and low levels of quasar activity. This region is largely unexplored and may hold clues to the crucial earlier stages of the co-evolution of black holes and galaxies.