  The dominating reionization source in the young universe has yet to be
identified. Possible candidates include metal poor starburst dwarf galaxies of
which the Blue Compact Galaxy Haro 11 may represent a local counterpart. Using
the Far Ultraviolet Spectroscopic Explorer (FUSE) we obtained spectra of Haro
11 to search for leaking ionizing radiation. A weak signal shortwards of the
Lyman break is identified as Lyman continuum (LyC) emission escaping from the
ongoing starburst. From profile fitting to weak metal lines we derive column
densities of the low ionization species. Adopting a metallicity typical of the
H II regions of Haro 11, the corresponding H I column density is optically
thick in the LyC. Therefore most of the LyC photons must escape through
transparent holes in the interstellar medium. Using spectral evolutionary
models we constrain the escape fraction of the produced LyC photons to between
4 and 10%, assuming a normal Salpeter IMF. We argue that in a hierarchical
galaxy formation scenario, this allows for a substantial contribution to cosmic
reionization by starburst dwarf galaxies at high redshifts.

Astrophysics