Building a map of orbits and dark matter in the Milky Way

01/29/2021 - 3:30pm to 4:30pm
Speaker(s) / Presenter(s): 
David W. Hogg (NYU)
Traditionally, measurements of the force law, the gravitational potential, and the mass distribution in the Milky Way (and other galaxies) have been based on snapshots—just contemporary positions and velocities—of stars and gas, whereas really precise dynamical models (of the Solar System, say) and really precise tests of gravity are only possible when we can see complete orbits (Newton's contemporaries inferred the inverse-square law from the shapes of orbits). In recent years we have figured out ways to make images of orbits in the outskirts of the Milky Way using streams of stars with common origins, and this year we have developed techniques to use the element abundances in stars—stellar chemical compositions—to link stars in different parts of the Milky Way disk but on the same orbits (just at different phases). These new techniques have the capability to deliver images of the orbit structure and hence the dark-matter distribution in the Milky Way. They will also reveal asymmetries, time dependence, and merger history. Based on work with Adrian Price-Whelan (Flatiron).
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