On Ly α emission in z ∼ 3-6 UV-selected galaxies

Abstract

Context. Determining Lyα properties of distant galaxies is of great interest for various astrophysical studies. Aims. We examine how the strength of Lyα emission can be constrained from broad-band SED fits instead of relying on spectroscopy. Methods. We use our SED-fitting tool, which includes the effects of nebular emission and considers in particular Lyα emission as a free parameter, and we demonstrate our method with simulations of mock galaxies. With this tool we analyse a large sample of U, B, V, and i dropout galaxies with multi-band photometry. Results. We find significant trends in the fraction of galaxies with Lyα emission increasing both with redshift z and towards fainter magnitude (at fixed z), and similar trends for the Lyα equivalent width. Our inferred Lyα properties are in good agreement with the available spectroscopic observations and other data. Conclusions. These results demonstrate that the strength of Lyα emission in distant star-forming galaxies can be inferred quantitatively from broad-band SED fits, at least statistically for sufficiently large samples with good photometric coverage. © 2011 ESO.