We compare elemental abundance patterns of \sim 200 extremely metal-poor ( EMP ; [ Fe/H ] < -3 ) stars with supernova yields of metal-free stars in order to obtain insights into the characteristic masses of the first ( Population III or Pop III ) stars in the Universe .
Supernova yields are prepared with nucleosynthesis calculations of metal-free stars with various initial masses ( M = 13 , 15 , 25 , 40 and 100 M _ { \odot } ) and explosion energies ( E _ { 51 } = E / 10 ^ { 51 } [ erg ] = 0.5 - 60 ) to include low-energy , normal-energy , and high-energy explosions .
We adopt the mixing-fallback model to take into account possible asymmetry in the supernova explosions and the yields that best-fit the observed abundance patterns of the EMP stars are searched by varying the model parameters .
We find that the abundance patterns of the EMP stars are predominantly best-fitted with the supernova yields with initial masses M < 40 M _ { \odot } , and that more than than half of the stars are best fitted with the M = 25 M _ { \odot } hypernova ( E _ { 51 } = 10 ) models .
The results also indicate that the majority of the primordial supernovae have ejected 10 ^ { -2 } -10 ^ { -1 } M _ { \odot } of ^ { 56 } Ni leaving behind a compact remnant , either a neutron star or a black hole , with mass in a range of \sim 1.5 - 5 M _ { \odot } .
The results suggest that the masses of the first stars responsible for the first metal-enrichment are predominantly < 40 M _ { \odot } .
This implies that the higher mass first stars were either less abundant or directly collapsing into a blackhole without ejecting heavy elements or that a supernova explosion of a higher-mass first star inhibits the formation of the next generation of low-mass stars at [ Fe/H ] < -3 .