A low escape fraction of ionizing photons of L>L* Lyman break galaxies at z=3.3

Understand

We present an upper limit for the relative escape fraction (f_{esc}^{rel}) of ionizing radiation at z~3.3 using a sample of 11 Lyman Break Galaxies (LBGs) with deep imaging in the U band obtained with the Large Binocular Camera, mounted on the prime focus of the Large Binocular Telescope.

• We selected 11 LBGs with secure redshift in the range 3.27<z<3.35, from 3 independent fields.
• We stacked the images of our sources in the R and U band, which correspond to an effective rest-frame wavelength of 1500\AA and 900\AA respectively, obtaining a limit in the U band image of >=30.7(AB)mag at 1 sigma.
• We derive a 1 sigma upper limit of f_{esc}^{rel}~5%, which is one of the lowest values found in the literature so far at z~3.3.