Peering into Galaxies with Gamma-Ray Glasses Dr. Craig Markwardt
U. Maryland and NASA/Goddard Space Flight Center Most galaxies are thought to have a supermassive black hole at their center, as a natural consequence of the formation of structure in the universe. Finding these black holes is not as easy as it may seem however, because the centers of galaxies are often shrouded by obscuring material, which preferentially absorb optical and X-ray light. Most active galaxies found by surveys in the optical and X-ray wavelengths will thus be biased toward unobscured objects. However, as we move towards shorter wavelength X-rays - "hard X-rays" - the obscuring clouds become transparent. We have exploited this fact to construct a survey of all local active galaxies with the Swift Burst Alert Telescope, free of previous biases. While Swift and BAT were designed to chase and study gamma-ray bursts, the most powerful explosions in the universe, BAT is able to pierce the veil of obscuration surrounding local galaxies as well. I will present a summary of these results and compare to the properties of the supermassive black hole at the center of our own galaxy.

Location: Physics Bldg., room 401