32) Highlights from a comprehensive survey of stellar streams in the Milky Way's halo

Abstract: Stellar streams in galactic halos provide a snapshot in time of the process of hierarchical accretion by which galaxies grow. In recent years, wide-area photometric surveys have revealed a wealth of stellar substructure in the Milky Way's halo. Since 2018 we have been working with international collaborators on the first complete spectroscopic census of southern hemisphere streams with 2df+AAOmega on the AAT. Thus far, we have obtained 6D+1 phase space information for 10 streams in the DES footprint, and we have expanded our program beyond the DES footprint to cover more southern streams. The radial velocities and stellar metallicities from our spectra - together with proper motions from Gaia DR2 - provide us with a unique dataset for understanding the Milky Way's halo. We are investigating stellar populations in the halo, the progenitors and formation processes of the streams, the accretion history of our Galaxy, the mass and overall morphology of the Milky Way's gravitational potential, and ultimately the nature of dark matter. I will give an overview of our program and present highlights from our science results on stream progenitors and orbits, as well as the serendipitous discovery of a main sequence hypervelocity star ejected from the Galactic centre via the Hills mechanism.

Bio: Associate Professor Daniel Zucker is an observational astronomer, studying Milky Way and Local Group stellar populations as a key to understanding galaxy formation and evolution in general. He received his PhD from the University of Washington in Seattle, and after postdocs in Germany (MPIA) and the UK (Cambridge), he joined Macquarie University in 2009. He was previously an Australian Research Council Future Fellow, and is currently a Councilor of the Astronomical Society of Australia and a member (and immediate past chair) of its IDEA (Inclusion, Diversity and Equity in Astronomy) steering committee.