Colloquium by Sarah Pearson, NYU
In the coming decade, thousands of stellar streams will be observed around the halos of external galaxies with the Nancy Grace Roman Space Telescope, Euclid, and the Vera C. Rubin Observatory. Stellar streams form when a dwarf galaxy or a cluster of stars is torn apart due to an underlying galactic potential, leaving behind a swath of thousands of stars that exhibit coherent, ordered motion. These streams are sensitive to the distribution of dark matter and to the population of dark matter subhalos in galaxies, both of which depend on the mass and interactions of the dark matter particle. In this talk, I discuss the status of the search for dark matter and how we can use the incoming wealth of stellar stream data to rule out dark matter candidates. I first focus on stellar streams from accreted dwarf galaxies and present new models of the elliptical galaxy’s, Centaurus A’s, dwarf companion and its associated stellar stream. With a novel external galaxy stream-fitting technique, I show that there are many viable stream models that fit the data well, provided that Centaurus A has a dark matter halo mass larger than M_200 > 4.7 x 10^12 Msun. I also demonstrate that just one radial velocity measurement breaks degeneracies between stream morphology and dark matter halo mass. In the second part of the talk, I discuss stellar streams from globular clusters. Due to their low velocity dispersions, these streams are sensitive to gravitational interactions with low-mass dark matter subhalos. In the Milky Way, we know of a handful of stellar streams with noticeable under-densities, however, the Galactic bar, molecular clouds, and spiral arms can also lead to similar signatures in the streams. To rule out dark matter particle candidates with stellar streams, we need to go beyond the Milky Way. If we can instead find globular cluster streams in external galaxies without these baryonic perturbers, gaps in such streams can serve as a test of LCDM.
Followed by wine and cheese.
Host: Kathryn Johnston