Far-infrared observations of dust in Ly α emitters at z ≈ 2–6

Journal article, 2026

The bright Ly (Formula presented) line is regularly used to identify high-redshift star-forming galaxies known as Ly (Formula presented) emitters (LAEs). However, Ly (Formula presented) is affected by resonant scattering and dust absorption making interpretation of its brightness challenging without additional observations. We use SCUBA-2, PACS and SPIRE data to investigate the far-infrared emission, Ly (Formula presented) escape fraction [(Formula presented) )]and infrared excess ((Formula presented) ) in (Formula presented) 4000 LAEs at (Formula presented) –6 from SC4K. Five LAEs, all hosting AGN, are individually detected with fluxes (Formula presented) –5.5 mJy at 850 (Formula presented) m. Stacking is used to probe the average emission from all individually-undetected LAEs, though the stacks are undetected at all wavelengths (e.g. (Formula presented)  mJy; (Formula presented) ). We group the sample into bins of redshift, stellar mass, Ly (Formula presented) luminosity and AGN status. Most subsets are undetected but LAEs containing AGN and that have high stellar masses ((Formula presented) ; including and excluding AGN) are detected at most wavelengths, suggesting that stellar mass and AGN heating may be enhancing the dust visibility. Individually detected LAEs and detected stacks have (Formula presented)  per cent–7 per cent, while all undetected stacks (Formula presented). All LAEs together average over (Formula presented) and display significant scatter, suggesting a clumpy ISM dust distribution. Non-zero (Formula presented) in massive and AGN-hosting LAEs suggests ionizing photons may escape even from dusty galaxies, challenging the idea that dusty galaxies are poor leakers. Examination of the IRX–(Formula presented) relation shows LAEs have higher IRX than typical star-forming galaxies at similar redshifts. However, our detections tend to favour more massive, AGN-hosting systems and deeper observations are therefore needed.