Can Population III stars be major origins of both merging binary black holes and extremely metal poor stars?

Understand

Population (Pop) III stars, first stars, or metal-free stars are made of primordial gas.

• We have examined if they can be dominant origins of merging binary black holes (BHs) and extremely metal-poor stars.
• The abundance pattern of EMP stars is helpful to trace back the properties of Pop III stars.
• We have confirmed previous arguments that the observed BH merger rate needs Pop III star formation efficiency 10 times larger than theoretically predicted values, while the cosmic reionization history still permits such a high Pop III star formation efficiency.