The Acceleration Discrepancy
Monday's speaker will be Professor Stacy McGaugh. Professor McGaugh is the Chair of the Department of Astronomy and the Director of the Warner and Swasey Observatory at Case Western Reserve University in Cleveland, Ohio. He is a prominent expert on low surface brightness galaxies and the observational evidence associated with dark matter and theories of modified gravity. He has also occasionally constructed theoretical models for predicting features of galaxies, galaxy groups, and the early Universe. A tentative description of what he will be telling us about is below, with the caveat that he reserves the right to use the element of surprise.
"The dark matter problem has been with us for the better part of a century, but the missing mass remains at large. A central aspect of the problem is that the need for dark matter sets in at a characteristic acceleration scale. I will discuss the data indicating this scale, which was not recognized until after the current cold dark matter paradigm was established. Cold dark matter is scale-free, so the existence of the observed acceleration scale indicates a solution that differs from that which is widely presumed."
About Professor Stacy McGaugh
Professor Stacy McGaugh is an astronomer who studies galaxies, dark matter, and theories of modified gravity. He is an expert on low surface brightness galaxies, a class of objects in which the stars are spread thin compared to bright galaxies like our own Milky Way. He demonstrated that these dim galaxies appear to be dark matter dominated, providing unique tests of theories of galaxy formation and modified gravity. He also showed that they obeyed the Tully-Fisher relation once gas was included along with stars in the mass budget, coining the term "Baryonic Tully-Fisher relation."
Together with Jim Schombert and Federico Lelli, McGaugh has assembled the SPARC database of galaxies with rotation curves and Spitzer surface photometry. Together, these provide accurate mass models for nearly 200 rotationally supported disk galaxies, mapping the distribution of their mass components in detail, and providing the most accurate assessment of the stellar mass of galaxies currently available. The SPARC database has been widely used by other, and has become a touchstone for many theoretical as well as observational investigations.
In addition to his observational work, he has also played theorist on occasion, successfully predicting the velocity dispersions of dwarf galaxies like Crater 2 and Andromeda 28 (and many other Local Group dwarfs), the declining slope of the rotation curve of the Milky Way, the stability properties of low surface brightness disks, the early reionization of the universe and the strong absorption signal observed in the EDGES experiment, and the first-to-second peak amplitude ratio of the acoustic power spectrum of the cosmic microwave background.
McGaugh studied at MIT, Princeton, and the University of Michigan. He is a distinguished alumnus of both Flint (MI) Northern High School and the Astronomy department of the University of Michigan. McGaugh was a research fellow at the Institute of Astronomy at the University of Cambridge, the Department of Terrestrial Magnetism of the Carnegie Institution of Washington, and Rutgers before joining the faculty of the University of Maryland in 1998. In 2012, he moved to Case Western Reserve University where he is currently the Chair of the Department of Astronomy and Director of the Warner and Swasey Observatory.