Are Active Galactic Nuclei accretion disks too big?

Wayne State University, Detroit MI

Investigators

Abstract

Part 1 All major galaxies appear to harbor a supermassive black hole, millions of times the mass of our Sun, residing at their center. These black holes have an important influence over the way their host galaxies grow and evolve. An important way in which the black hole grows is through a process called accretion, where hot gas spirals into the black hole via a disk. Recent studies suggest that these accretion disks are several times larger than expected by theory. As these objects are so distant astronomers cannot take direct pictures of the disks themselves and so must use indirect techniques. In this project, the PI will use a technique called reverberation mapping. This uses echoes of light to determine the size of the accretion disks, much like sonar uses echoes of sound to map the ocean floor. Using a dedicated robotic telescope the PI will monitor approximately 10 supermassive black hole accretion disks per year to test why accretion disks appear too big, and better understand how black holes grow. In the area of Broader Impacts, the PI will integrate the science of this project into local Detroit schools. Part 2 Supermassive black holes play an important role in the growth and evolution of the galaxies in which they reside. A principal way in which they grow is via the accretion of gas via a disk. However, observational probes of the structure of these accretion disks are rare, especially since they are too small and distant to spatially resolve directly. In this project, the PI will use a technique known as reverberation mapping which measures echoes of light to determine the size scale of the accretion disks. Several recent studies using this technique suggest that these disks are a factor of 2 - 3 larger than expected. To better understand this we will use a dedicated robotic telescope to monitor approximately 10 supermassive black hole accretion disks per year building a substantial sample. Furthermore, the PI will apply novel analysis techniques to further test of origin of the echoes, and test why these accretion disks appear too big. In the area of Broader Impacts, the PI will integrate the science of this project into local Detroit schools. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.