2011/04/27 by K. Boutsia, A. Grazian, E. Giallongo +12 · 2 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #Background radiation #Galaxies: Formation, Evolution, Phenomena #Galaxy #Ionization #Large Binocular Telescope #Limit (mathematics) #Lyman limit #Redshift #Sigma #astro-ph.GA
paper · pdf · doi:10.1088/0004-637x/736/1/41
15 pages, 2 figures, 1 table, accepted for publication in ApJ
arxiv created 2011/04/27 · openalex publication_date 2011/07/05 · arxiv updated 2015/05/28 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We present an upper limit for the relative escape fraction ( f rel esc ) 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 redshifts in the range 3.27 < z < 3.35, from three independent fields. We stacked the images of our sources in the R and U bands, which correspond to an effective rest-frame wavelength of 1500 Å and 900 Å, respectively, obtaining a limit in the U band image of ⩾30.7 mag (AB) at 1σ. We derive a 1σ upper limit of f rel esc ∼ 5%, which is one of the lowest values found in the literature so far at z ∼ 3.3. Assuming that the upper limit for the escape fraction that we derived from our sample holds for all galaxies at this redshift, the hydrogen ionization rate that we obtain (Γ −12 < 0.3 s −1 ) is not enough to keep the intergalactic medium ionized and a substantial contribution to the UV background by faint active galactic nuclei is required. Since our sample is clearly still limited in size, larger z ∼ 3 LBG samples at similar or even greater depths are necessary to confirm these results on a more firm statistical basis.