A LOW ESCAPE FRACTION OF IONIZING PHOTONS OF L > L* LYMAN BREAK GALAXIES AT z = 3.3
- INAF-Osservatorio Astronomico di Roma, Via Frascati 33, I-00040, Monteporzio (Italy)
- INAF-Osservatorio Astronomico di Bologna, Via Ranzani 1, I-40127, Bologna (Italy)
- INAF-Osservatorio Astronomico di Trieste, Via G.B. Tiepolo 11, I-34131, Trieste (Italy)
- Institute of Astronomy, ETH Zuerich, CH-8093, Zuerich (Switzerland)
We present an upper limit for the relative escape fraction (f{sup rel}{sub esc}) of ionizing radiation at z {approx} 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 A and 900 A, respectively, obtaining a limit in the U band image of {>=}30.7 mag (AB) at 1{sigma}. We derive a 1{sigma} upper limit of f{sup rel}{sub esc} {approx} 5%, which is one of the lowest values found in the literature so far at z {approx} 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 ({Gamma}{sub -12} < 0.3 s{sup -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 {approx} 3 LBG samples at similar or even greater depths are necessary to confirm these results on a more firm statistical basis.
- OSTI ID:
- 21578322
- Journal Information:
- Astrophysical Journal, Vol. 736, Issue 1; Other Information: DOI: 10.1088/0004-637X/736/1/41; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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