Abstract: The process of galaxy formation alters the phase-space distribution of the dark matter and stellar components of the Milky Way halo. Debris from accretion is apparent as spatial overdensity at the beginning. After several billion years, those pieces of debris are spread over several tens of kpc. Thus, one cannot expect to find many of the halo streams predicted as spatially coherent structures in the solar neighborhood. However, the phase-space structures of those streams provide hints about their common origin. The origins of these halo streams play an important role in understanding the formation of our Milky Way. In this talk, I will present our detections of new evidence for a merging history of our Milky Way during its formation. Simulations predict one dwarf galaxy might correspond to multiple streams detected in phase space and there should be hundreds of streams in the solar neighborhood. LAMOST provides an unprecedentedly large sample and will contribute to more and more detections of halo streams in the future.

Bio: Prof. Gang Zhao was awarded Ph. D. in Astrophysics in Nanjing University as a joint training student with the European Southern Observatory in 1990. He is the leading professor of NAOC, Chairman of LAMOST Science Committee, Director of the Key Lab of Optical Astronomy, CAS.

Prof. Zhao has been devoting himself to observational astronomy for over 20 years. He has taken the lead in detailed quantitative analysis of chemical elements based on a large sample of high-resolution spectra of metal-poor dwarfs. He also gave a new empirical formula of the influence of neutral hydrogen collision for NLTE analysis. Meanwhile, he began the research of chemical abundance of extra-solar planetary systems. Prof. Zhao was honored with the Second Prize of National Natural Science in 2008, as well as winner of the Science and Technology Award of the Ho Leung Ho Lee Foundation in 2010.