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Understanding the escape of ionizing (Lyman continuum) photons from galaxiesis vital for determining how galaxies contributed to reionization in the earlyuniverse. While directly detecting Lyman continuum from high redshift galaxiesis impossible due to the intergalactic medium, low redshift galaxies inprinciple offer this possibility, but requirie observations from space. Thefirst local galaxy for which Lyman continuum escape was found is Haro11 , aluminous blue compact galaxy at z=0.02, where observations with the FUSEsatellite revealed an escape fraction of 3.3 %. However the FUSE aperturecovers the entire galaxy, and it is not clear from where the Lyman continuum isleaking out. Here we utilize HST/COS spectroscopy in the wavelength range1100-1700 A of the three knots (A, B, and C) of Haro11 to study the presence ofLy-$\alpha$ emission and the properties of intervening gas. We find that allknots have bright Ly-$\alpha$ emission. UV absorption lines, originating in theneutral interstellar medium, as well as lines probing the ionized medium, areseen extending to blue shifted velocities of 500 km/s in all three knots,demonstrating the presence of an outflowing multiphase medium. We find thatknots A and B have large covering fractions of neutral gas, making LyC escapealong these sightlines improbable, while knot C has a much lower coveringfraction ($\lesssim50$%). Knot C also has the the highest Ly-$\alpha$ escapefraction and we conclude that it is the most likely source of the escapingLyman continuum detected in Haro11.

The source of leaking ionizing photons from Haro11 -- Clues from HST/COS spectroscopy of knots A, B and C