Talk by Sarah Pearson – University of Copenhagen

Talk by Sarah Pearson

On June 19 2014, DARK's visitor Sarah Pearson is giving a talk at 14:15 in the DARK Lounge.

Title: Tidal Stream Morphology as a Milky Way Potential Probe: The Case of Palomar 5


Cosmological simulations of the large scale structure of the Universe, predict that all galaxies should lie within triaxial dark matter halos. In this talk, I present recent results from dynamical models of the globular cluster, Palomar 5 (Pal 5), generated through N-body simulations. The overall goal of this work is to investigate the shape of our own Galaxy's dark matter halo. Pal 5 was the first globular cluster for which associated extended, cold streams of stars were found, now mapped over 22 degrees across the sky. In our simulations Pal 5’s position, distance and radial velocity are fixed by observations and proper motion allowed to freely vary. When these models are run within a Milky-Way-like potential consisting of a disk and bulge surrounded by a spherical dark matter halo, cases can be found that match the morphology and orientation as well as all current line-of-sight velocity measurements of the streams. However, when we represent the dark matter halo by the triaxial potential for the Milky Way proposed by Law & Majewski (2010) instead, no model can be found where thin streams align with those observed for Pal 5. Our results demonstrate that the morphology of Pal 5 alone can be used to rule out the Law & Majewski potential model. In addition, they demonstrate that the existence and location of thin streams more generally provide broad but powerful constraints on the shape and orientation of the Milky Way potential on large scales, without the need for additional dimensions of information. This represents a novel approach to investigating how matter is distributed on large scales around the Milky Way.