Special Physics Colloquium: Wednesday, March 6, 2019 -- Decoding the Milky Way galaxy

Event Date: 

Wednesday, March 6, 2019 - 4:00pm

Event Location: 

  • KITP Main Seminar Room
  • Special Physics Colloquium

Stars residing in the Milky Way halo hold the key to the origin of our Galaxy. The stellar halo has traditionally been inaccessible as it contains only one percent of stars in the Galaxy, but novel data sets have recently enabled us to confidently identify thousands of halo stars. Stellar maps of the Milky Way halo are extremely structured and reveal individual progenitors of our Galaxy as coherent, tidally distorted features. A Fisher analysis indicates that the 6-dimensional distribution of such tidal debris constrains the mass enclosed within its current location in the Galaxy. I will discuss how the forward-modeling framework I developed for individual structures can be extended to build a hierarchical model for a network of such objects. This inference will reconstruct the three-dimensional distribution of the otherwise elusive dark matter in the Milky Way. In addition to tracing the underlying distribution of matter, the stellar halo retains an archaeological record of a galaxy's history. I will show that the conserved orbital quantities of halo stars can be used to discover even the oldest, completely dissolved, progenitors of the Milky Way, and thus also provide a unique window into the early universe.


Ana Bonaca, Harvard