Hubble imaging of the ionizing radiation from a star-forming galaxy at Z = 3.2 with f(esc) > 50%

Star-forming galaxies are considered to be the leading candidate sources dominating cosmic reionization at z > 7: the search for analogs at moderate redshift showing Lyman continuum (LyC) leakage is currently an active line of research. We have observed a star-forming galaxy at z = 3.2 with Hubble/WFC3 in the F336W filter, corresponding to the 730-890 angstrom rest-frame, and detected LyC emission. This galaxy is very compact and also has a large Oxygen ratio [O III] lambda 5007/[O II] lambda 3727 (greater than or similar to 10). No nuclear activity is revealed from optical/near-infrared spectroscopy and deep multi-band photometry (including the 6Ms X-ray Chandra observations). The measured escape fraction of ionizing radiation spans the range 50%-100%, depending on the intergalactic medium (IGM) attenuation. The LyC emission is measured at m(F336W) = 27.57 +/- 0.11 (with signal-to-noise ratio (S/N) = 10) and is spatially unresolved, with an effective radius of R-e 7, allowing a direct comparison with the lower-redshift LyC emitters, such as that reported here.