The Supersonic Project: Star Formation in Early Star Clusters without Dark Matter

TL;DR

This study uses cosmological simulations to demonstrate that SIGOs, formed due to baryon-dark matter relative motion, can efficiently form stars and evolve into globular cluster-like objects within dark matter halos.

Contribution

It provides the first detailed simulation-based evidence that SIGOs can form stars and become globular clusters without dark matter halos, offering a new formation pathway.

Findings

SIGOs form stars despite lacking dark matter halos

Star clusters from SIGOs are quickly accreted into dark matter halos

SIGOs could be observable as early globular clusters with JWST

Abstract

The formation mechanism of globular clusters (GCs) has long been debated by astronomers. It was recently proposed that Supersonically Induced Gas Objects (SIGOs), which formed in the early Universe due to the supersonic relative motion of baryons and dark matter at recombination, could be the progenitors of early globular clusters. In order to become GCs, SIGOs must form stars relatively efficiently despite forming outside of dark matter halos. We investigate the potential for star formation in SIGOs using cosmological hydrodynamic simulations, including the aforementioned relative motions of baryons and dark matter, molecular hydrogen cooling in primordial gas clouds, and including explicit star formation. We find that SIGOs do form stars and that the nascent star clusters formed through this process are accreted by dark matter halos on short timescales (a few hundreds of Myr). Thus, SIGOs may be found as intact substructures within these halos, analogous to many present-day GCs. From this result, we conclude that SIGOs are capable of forming star clusters with similar properties to globular clusters in the early Universe and we discuss their detectablity by upcoming JWST surveys.