APEC Seminar (Astronomy - Particle Physics - Experimental Physics - Cosmology)

Speaker: Ana Bonaca (Harvard)
Title: Dynamical evidence for a dark substructure in the Milky Way halo
Date (JST): Wed, Jul 10, 2019, 15:30 - 16:30
Place: Seminar Room A
Related File: 2346.pdf
Abstract: Stars escaping globular clusters form thin, long and kinematically-cold tidal streams. In pristine conditions, these streams have nearly uniform density, however, new Gaia observations of one such structure in the Milky Way halo have revealed a likely site of perturbation. The on-sky morphology suggests a recent, close encounter with a massive and dense perturber. Known baryonic objects are unlikely perturbers based on their orbital properties, but observations permit a low-mass dark-matter subhalo as a plausible candidate. This observation opens up the possibility that detailed observations of streams could measure the mass spectrum of dark-matter substructures and even identify individual substructures and their orbits in the Milky Way halo.