Extreme damped Lyman-$\alpha$ absorption in young star-forming galaxies at $z=9-11$

Understand

The onset of galaxy formation is thought to be initiated by the infall of neutral, pristine gas onto the first protogalactic halos.

• However, direct constraints on the abundance of neutral atomic hydrogen (HI) in galaxies have been difficult to obtain at early cosmic times.
• Here we present spectroscopic observations with JWST of three galaxies at redshifts $z=8.8 - 11.4$, about $400-600$ Myr after the Big Bang, that show strong damped Lyman-$\alpha$ absorption ($N_{\rm HI} > 10^{22}$ cm$^{-2}$) from HI in their local surroundings, an order of magnitude in excess of the Lyman-$\alpha$ absorption caused by the neutral intergalactic medium at these redshifts.
• Consequently, these early galaxies cannot be contributing significantly to reionization, at least at their current evolutionary stages.