Institute for Advanced Study Informal Astrophysics Seminar

As clusters of stars orbit our own Milky Way, a gravitational tidal interaction unfolds and the clusters tear apart into distinct morphological and kinematic structures. From our understanding of gravity, the distribution and motion of these stellar structures enable us to work backwards in time and thereby study our Milky Way's past and evolution. Stellar streams additionally provide promising prospects for detecting dark matter substructure through disturbances in the streams’ structure - for example in the form of distinct under densities in their stellar distributions. Palomar 5 (Pal 5) is an old globular cluster orbiting our Galaxy, while disrupting into thin leading and trailing stellar arms. In this talk, I will show that a previous encounter between the Pal 5 stellar stream and the Milky Way’s Galactic bar has punched a hole in the stream, which can explain new observations finding that leading arm of Pal 5 appears to be a lot shorter than the trailing arm. My work implies that caution should be applied before interpreting stream gaps as evidence for dark matter subhalos. Additionally, I will discuss ongoing work on the Milky Way’s Galactic bar and what we might learn about the bar through its interaction with stellar streams, through simulations of dwarf galaxies interacting with the Milky Way’s disk and by using Gaia DR2.