报告摘要：Stellar streams are one of the most powerful tracers to determine the mass of the Milky Way and other nearby galaxies. Full 6D phase space data is necessary for us to get there. In this talk, I will discuss two ongoing spectroscopic programs to study the stellar streams in our Milky Way and highlight a few latest scientific results from these two programs. The Southern Stellar Stream Spectroscopic Survey (S5), started in 2018, is the first systematic program pursuing a complete census of known streams in the Southern Hemisphere using the fiber-fed AAOmega spectrograph on the Anglo-Australian Telescope. The science results from S5 include a homogeneous study of the kinematic and chemical properties of dozen streams in our Milky Way, the finding of a stream at ~30 kpc possibly perturbed by the dark matter subhalo, the constraints on the mass of the Milky Way and the Large Magellanic Cloud with stellar streams, and the discovery of the fastest hyper velocity stars ejected from Galactic center that can be used to study the shape of the Milky Way halo. The Milky Way Survey of the Dark Energy Spectroscopic Instrument (DESI), on the other hand, is a recently started 5-yr spectroscopic program in the Northern Hemisphere. DESI deploys 5000 fibers over a 3.2 deg diameter field of view at the prime focus of the Mayall 4-meter telescope at the Kitt Peak National Observatory, with a spectral resolution of R~2500-5000 and a wavelength coverage of 3600-9824 Angstrom. With just the first year of data collected in 2021-2022, 4 million unique stars have been observed, including many stars in the streams of the northern sky (e.g. GD-1) and showing some interesting features. We are entering an extremely data-rich era in the next decade, with full 6D+chemistry information on dozens of stellar streams, to shape our understanding on the chemo-dynamical evolution of the Milky Way, as well as the nature of the dark matter.

主讲人简介：Ting Li is an Assistant Professor at the David A. Dunlap Department of Astronomy & Astrophysics. Ting’s research focuses on near-field cosmology. In particular, she studies the stars in the Milky Way Galaxy and nearby galaxies to understand how they form and to understand the nature of dark matter. She specializes in analyzing large data sets from imaging surveys of wide areas the sky and also performs traditional astronomical observations with optical and near-infrared telescopes. Ting also builds astronomical instruments and contributes to infrastructure work for large-area sky surveys such as the Dark Energy Survey (DES), Dark Energy Spectroscopic Instrument (DESI) and others. She is the founder and leader of the Southern Stellar Stream Spectroscopic Survey, a survey to map streams of stars in the sky visible from the southern hemisphere to determine the mass profile of the Milky Way. She is one of the Dark Matter Working Group co-chairs of the Maunakea Spectroscopic Explorer, a 11.25-meter telescope facility dedicated to the next generation spectroscopic surveys. Ting grew up in Shanghai, China, where she completed her bachelor’s degree at Fudan University, with a major in physics and a minor in diplomacy. She received the Eramus Mundus Scholarship for a Joint European Master Program in Space Science and Technology. She earned her PhD in physics from Texas A&M University in 2016, and was selected as the 2016 recipient of the Leon Lederman fellow at Fermi National Accelerator Laboratory. She was a NASA Hubble Fellowship Program Einstein Fellow and Carnegie-Princeton Fellow at Carnegie Observatories in 2019-2021