(Proposal ID) S16A-119

(PI) Aoki, Wako

(Proposal Title)
LAMOST/Subaru study for 500 very metal-poor stars

(Abstract)
Surveys of very metal-poor stars and follow-up spectroscopic studies for them 
in the past decade have provided with rich information on the nature of first 
stars and early chemical evolution of the Milky Way Galaxy. The studies are, 
however, still based on small size of samples, in particular for the lowest 
metallicity range, compared to the sample size required for understanding the 
indication of the observational facts obtained by previous studies (e.g., 
existence of stars with [Fe/H]<-5, stars with low abundance of alpha-elements) 
in the context of galaxy formation and evolution. We propose to obtain high-
resolution spectra with Subaru/HDS for 500 candidates of very metal-poor stars 
found with LAMOST. This program will almost double the sample size for 
[Fe/H]<-2 for which abundances of important elements (e.g., C, Mg, Ca, Sr, Ba) 
are determined, and enable us to study the statistics of abundance 
distributions of alpha, iron-peak and neutron capture elements as well as Li 
and C. The large sample also provides a list of stars having anomalous 
abundances (e.g., alpha-rich/poor stars, super Li-rich red giants), which are 
useful to probe the enrichment in the early Galaxy and low-mass star evolution 
with very low metallicity.