Massive Population III Galaxies Near a GN-z11 Analog: The Role of the Baryon-Dark Matter Streaming Velocity

Abstract

Recently the James Webb Space Telescope (JWST) detected Hebe, a Population III (Pop III) candidate located ${\sim}3$ kpc in projection from the massive $z=10.6$ galaxy GN-z11. This raises the question of whether Pop III star formation is expected in the vicinity of massive high-redshift galaxies or whether it would be prevented by early metal enrichment. We address this with a semi-analytic model of Pop III and metal-enriched star formation applied to a zoom-in N-body simulation of a highly overdense region surrounding a GN-z11 analog. The zoom-in region resolves the minihalos where the first stars form. We find that Pop III and metal-enriched star formation both occur earlier, and with a higher star formation rate density, than in a typical mean-density environment. The majority of Pop III star formation in minihalos ends by $z\sim15$; however, we identify a distinct population of late-forming Pop III galaxies that form near the central galaxy. These systems have their star formation delayed due to ionizing feedback from the central GN-z11 analog and experience a Lyman-Werner (LW) intensity of ${\sim}10$ - $100~J_{21}$, potentially leading to massive Pop III starbursts similar to Hebe. Interestingly, the abundance of these Pop III galaxies depends strongly on the baryon-dark matter streaming velocity, $v_{\rm bc}$, because a higher streaming velocity allows halos to remain chemically pristine for longer. None of these late-forming Pop III sources occur for $v_{\rm bc}=0$, while many form at high $v_{\rm bc}$. Averaging over the expected distribution of streaming velocities, we predict that of order four GN-z11-like galaxies would need to be surveyed at $z\sim11$ to expect to find one such source. We also note these environments may provide a natural formation site for heavy black hole seeds.