James Webb Space Telescope Feed Post

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

Paper abstract: 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. Simulations of galaxy formation show that such massive gas reservoirs surrounding young galaxies so early in the history of the universe is a signature of galaxy formation in progress.