Extremely metal poor stars and Chemical Evolution in the Early Universe

paper) stars are stars formed in the early universe in terms of chemical evolution. They are formed at high redshift but are still shining with the glow of nuclear burning in the Local Group. Hundreds of the EMP stars has been identified in the Milky Way halo and element abundances of these stars are revealed by follow-up spectroscopic observations. They provide a means of probing the earliest phases of the evolution of the Milky Way and supernovae in the early universe. Among them, two hyper metal-poor (HMP) stars with [Fe/H] < −5 are the most metal deficient objects observed yet. In our previous study[1], we give constraint on the initial mass function (IMF) of the EMP stars and argue that typical mass of EMP stars is ~10M�. Changeover of the IMF affects the chemical evolution of the Milky Way