title: Eight per cent leakage of Lyman continuum photons from a compact, star-forming dwarf galaxy.
abstract: One of the key questions in observational cosmology is the identification of the sources responsible for ionization of the Universe after the cosmic 'Dark Ages', when the baryonic matter was neutral. The currently identified distant galaxies are insufficient to fully reionize the Universe by redshift z ≈ 6 (refs 1-3), but low-mass, star-forming galaxies are thought to be responsible for the bulk of the ionizing radiation. As direct observations at high redshift are difficult for a variety of reasons, one solution is to identify local proxies of this galaxy population. Starburst galaxies at low redshifts, however, generally are opaque to Lyman continuum photons. Small escape fractions of about 1 to 3 per cent, insufficient to ionize much surrounding gas, have been detected only in three low-redshift galaxies. Here we report far-ultraviolet observations of the nearby low-mass star-forming galaxy J0925+1403. The galaxy is leaking ionizing radiation with an escape fraction of about 8 per cent. The total number of photons emitted during the starburst phase is sufficient to ionize intergalactic medium material that is about 40 times as massive as the stellar mass of the galaxy.
authors.affiliation: Main Astronomical Observatory, National Academy of Sciences of Ukraine, 27 Zabolotnoho street, Kyiv 03680, Ukraine.
authors.forename: Y I
authors.initials: YI
authors.lastname: Izotov
authors.affiliation: Astronomical Institute, Czech Academy of Sciences, Bocˇní II 1401, 141 00 Prague, Czech Republic.
authors.forename: I
authors.initials: I
authors.lastname: Orlitová
authors.affiliation: Observatoire de Genève, Université de Genève, 51 Chemin des Maillettes, 1290 Versoix, Switzerland.|CNRS, IRAP, 14 Avenue East Belin, 31400 Toulouse, France.
authors.forename: D
authors.initials: D
authors.lastname: Schaerer
authors.affiliation: Astronomy Department, University of Virginia, PO Box 400325, Charlottesville, Virginia 22904, USA.
authors.forename: T X
authors.initials: TX
authors.lastname: Thuan
authors.affiliation: Observatoire de Genève, Université de Genève, 51 Chemin des Maillettes, 1290 Versoix, Switzerland.
authors.forename: A
authors.initials: A
authors.lastname: Verhamme
authors.affiliation: Main Astronomical Observatory, National Academy of Sciences of Ukraine, 27 Zabolotnoho street, Kyiv 03680, Ukraine.
authors.forename: N G
authors.initials: NG
authors.lastname: Guseva
authors.affiliation: Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany.
authors.forename: G
authors.initials: G
authors.lastname: Worseck