Title: Galactic Archaeology in the Era of Gaia and Large Spectroscopic Surveys

Speaker: Dr. Zhen Yuan (Shanghai Astronomical Observatory)

Time: 10:00pm, Mar. 12, 2021

Location: 5-516, PMO Xianlin Campus

Abstract: As the witnesses of the high redshift universe, dwarf galaxies, especially the low-mass ones, carry the imprint of essential physical processes, from the formation of the first stars to the formation of the first galaxies that shaped the universe into the one we observe today. The Milky Way stellar halo provides us with a unique and readily accessible reservoir of stellar debris from ancient dwarf galaxies merged in the past. In the current era of Gaia and large spectroscopic surveys, such as LAMOST and forthcoming WEAVE and 4MOST, the full 6-dimensional kinematic information is available for millions of nearby stars for the first time. In this talk, I will report a newly discovered stream (LMS-1) from a disrupted low mass dwarf galaxy, which is the third stream contributed to the inner stellar halo, after the Sagittarius and Cetus Streams found 10 - 20 years ago, all of which have fairly polar orbits. This raises the question that if the disrupted dwarf galaxies along polar orbits can maintain relatively coherent stream structures, similar to the formation mechanism of the vast polar structure of satellite galaxies.