A Multi-wavelength Study of the Massive Black Hole Sagittarius A* at the Galactic Center

Northwestern University, Evanston IL

Investigators

Abstract

Dr Yusef-Zadeh will use multiwavelength time-series observations to test two models to explain the flaring observed in the Milky Way's central radio source. According to the 'plasmon' model, blobs of radio-bright material move outwards from the central black hole, brightening at successively longer wavelengths as they become optically thin to their own synchrotron radiation. If the flares are instead caused by hot-spots in an accretion disk around the black hole, the source should brighten simultaneously at all wavelengths. Sub-millimeter observations would be taken in both the northern and southern sky with single-dish telescopes, and radio-telescope arrays would be used at centimeter wavelengths, to measure both total intensity and polarization over periods of several days. Data from two such campaigns in 2007 is now in hand, and another that includes observations with NASA's Chandra space telescope in the X-ray is scheduled for mid-2008. Future campaigns may include mid-infrared data from ESA's Herschel space telescope. Archival data from the Very Large Array will also be used. Theoretical work will include an extension of the plasmon model to predict polarization that arises from the anisotropic emitting region. Dr. Yusef-Zadeh has developed an interactive web client with problem-based exercises for undergraduate and adult-education classes. He will develop further exercises for this system, based around this project. He will also continue to coordinate a program of interdisciplinary science lectures for the public, to teach at Adler Planetarium, and to involve students in public outreach. A postdoc will be trained through involvement in the research.