We explore the possibility of observing Population III ( Pop III ) stars , born of the primordial gas .
Pop III stars with masses below 0.8 M _ { \odot } should survive to date though are not observed yet , but the existence of stars with low metallicity as [ { Fe } / { H } ] < -5 in the Milky Way halo suggests the surface pollution of Pop III stars with accreted metals from the interstellar gas after birth .
In this paper , we investigate the runaway of Pop III stars from their host mini-halos , considering the ejection of secondary members from binary systems when their massive primaries explode as supernovae .
These stars save them from the surface pollution .
By computing the star formation and chemical evolution along with the hierarchical structure formation based on the extended Press–Schechter merger trees , we demonstrate that several hundreds to tens of thousands of low-mass Pop III stars escape from the building blocks of the Milky Way .
The second and later generations of extremely metal-poor ( EMP ) stars are also escaped from the mini-halos .
We discuss the spatial distributions of these escaped stars by evaluating the distances between the mini-halos in the branches of merger trees under the spherical collapse model of dark matter halos .
It is demonstrated that the escaped stars distribute beyond the stellar halo with a density profile close to the dark matter halo , while the Pop III stars are slightly more centrally concentrated .
Some escaped stars leave the Milky Way and spread into the intergalactic space .
Based on the results , we discuss the feasibility of observing the Pop III stars with the pristine surface abundance .