Formation of GW190521 via gas accretion onto Population III stellar black hole remnants born in high-redshift minihalos

Understand

The recent gravitational wave merger event, GW190521, has challenged our understanding of the stellar-mass black hole (BH) formation.

• The primary and secondary BH are both inferred to fall inside the pair-instability (PI) mass gap.
• Here we propose that the formation of such binaries is possible through gas accretion onto the BH remnants of Population III (Pop~III) stars born in high-redshift ($z>10$) minihalos.
• Once the parent halo has grown to the atomic-cooling limit, even brief episodes of gas accretion in the dense central regions of the halo can increase the masses of Pop~III remnant BHs above the PI limit.