dc.contributor.author Marchi, F dc.contributor.author Pentericci, L dc.contributor.author Guaita, L dc.contributor.author Ribeiro, B dc.contributor.author Castellano, M dc.contributor.author Schaerer, D dc.contributor.author Hathi, NP dc.contributor.author Lemaux, BC dc.contributor.author Grazian, A dc.contributor.author Le Fèvre, O dc.contributor.author Garilli, B dc.contributor.author Maccagni, D dc.contributor.author Amorin, R dc.contributor.author Bardelli, S dc.contributor.author Cassata, P dc.contributor.author Fontana, A dc.contributor.author Koekemoer, AM dc.contributor.author Le Brun, V dc.contributor.author Tasca, LAM dc.contributor.author Thomas, R dc.contributor.author Vanzella, E dc.contributor.author Zamorani, G dc.contributor.author Zucca, E dc.date.accessioned 2017-04-05T11:04:40Z dc.date.available 2017-04-05T11:04:40Z dc.date.issued 2017 dc.identifier.issn 0004-6361 dc.identifier.uri https://www.repository.cam.ac.uk/handle/1810/263473 dc.description.abstract Determining the average fraction of Lyman continuum (LyC) photons escaping high redshift galaxies is essential for understanding how reionization proceeded in the z>6 Universe. We want to measure the LyC signal from a sample of sources in the Chandra Deep Field South (CDFS) and COSMOS fields for which ultra-deep VIMOS spectroscopy as well as multi-wavelength Hubble Space Telescope (HST) imaging are available. We select a sample of 46 galaxies at $z\sim 4$ from the VIMOS Ultra Deep Survey (VUDS) database, such that the VUDS spectra contain the LyC part of the spectra, that is, the rest-frame range $880-910\AA$. Taking advantage of the HST imaging, we apply a careful cleaning procedure and reject all the sources showing nearby clumps with different colours, that could potentially be lower-redshift interlopers. After this procedure, the sample is reduced to 33 galaxies. We measure the ratio between ionizing flux (LyC at $895\AA$) and non-ionizing emission (at $\sim 1500 \AA$) for all individual sources. We also produce a normalized stacked spectrum of all sources. Assuming an intrinsic average $L_{\nu}(1470)/L_{\nu}(895)$ of 3, we estimate the individual and average relative escape fraction. We do not detect ionizing radiation from any individual source, although we identify a possible LyC emitter with very high Ly$\alpha$ equivalent width (EW). From the stacked spectrum and assuming a mean transmissivity for the sample, we measure a relative escape fraction $f_{esc}^{rel}=0.09\pm0.04$. We also look for correlations between the limits in the LyC flux and source properties and find a tentative correlation between LyC flux and the EW of the Ly$\alpha$ emission line. Our results imply that the LyC flux emitted by $V=25-26$ star-forming galaxies at z$\sim$4 is at most very modest, in agreement with previous upper limits from studies based on broad and narrow band imaging. dc.description.sponsorship This work is supported by funding from the European Research Council Advanced Grant ERC–2010–AdG–268107–EARLY and by INAF Grants PRIN 2010, PRIN 2012 and PICS 2013. AC, OC, MT and VS acknowledge the grant MIUR PRIN 2010– 2011. This work is based on data products made available at the CESAM data center, Laboratoire d’Astrophysique de Marseille. R.A. acknowledges support from the ERC Advanced Grant 695671 'QUENCH'. dc.language English dc.language.iso en dc.publisher EDP Sciences dc.title New constraints on the average escape fraction of Lyman continuum radiation in z ∼ 4 galaxies from the VIMOS Ultra Deep Survey (VUDS) dc.type Article prism.publicationDate 2017 prism.publicationName Astronomy and Astrophysics prism.volume 601 dc.identifier.doi 10.17863/CAM.8817 dcterms.dateAccepted 2016-12-23 rioxxterms.versionofrecord 10.1051/0004-6361/201630054 rioxxterms.version VoR rioxxterms.licenseref.uri http://www.rioxx.net/licenses/all-rights-reserved rioxxterms.licenseref.startdate 2017-05-01 dc.contributor.orcid Amorin Barbieri, Ricardo [0000-0001-5758-1000] dc.identifier.eissn 1432-0746 rioxxterms.type Journal Article/Review pubs.funder-project-id European Research Council (695671) cam.issuedOnline 2017-05-04
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