The main observational signature of star-forming galaxies at the highest redshifts is the Lyman-α (Lyα) emission line. But Lyα photons scatter in the neutral interstellar medium of their host galaxies, and may therefore be greatly absorbed by interstellar dust. It is now shown that the average escaping fraction of Lyα photons from star-forming galaxies at redshift z = 2.2 is just 5 per cent. This implies that numerous conclusions based on Lyα-selected samples will require upwards revision by an order of magnitude.
- Matthew Hayes
- Göran Östlin
- Jens Melinder