The 21-cm BAO signature of enriched low-mass galaxies during cosmic reionization

Understand

Studies of the formation of the first stars have established that they formed in small halos of $\sim 10^5 - 10^6 M_{\odot}$ via molecular hydrogen cooling.

• Since a low level of ultraviolet radiation from stars suffices to dissociate molecular hydrogen, under the usually-assumed scenario this primordial mode of star formation ended by redshift $z \sim 15$ and much more massive halos came to dominate star formation.
• However, metal enrichment from the first stars may have allowed the smaller halos to continue to form stars.
• In this Letter we explore the possible effect of star formation in metal-rich low-mass halos on the redshifted 21-cm signal of neutral hydrogen from $z = 6-40$.