First Stellar cluster formation at z = 15 - 25

The formation of Pop III stars and first stellar clusters can be affected by a cosmological effect, relative baryon-dark matter velocities, which is supersonic and driven by Baryon Acoustic Oscillation (Tseliakovich & Hirata10). The relative velocities influence the structure formation and can delay the formation of the first stars at z ~ 25 - 15 (e.g., Greif+11, Stacy+11). Nakazato+22 perform cosmological simulations including the relative velocity and non-equilibrium chemistry. I show that the supersonic relative velocity can expel the gas from the host halo and form dark matterless dense clouds with M ~ 10^6 Msun (Figure 1), which reach Jeans unstable and are expected to collapse and start star formation. This might be a new pathway of proto-globular clusters as suggested analytically by Naoz & Narayan 14. The research is expanded as a “supersonic project” a collaboration with UCLA, and I contribute to four co-authors’ papers.