  Around 400 million years after the Big Bang, the ultraviolet emission from
star-forming galaxies reionized the Universe. Ionizing radiation (Lyman
Continuum, LyC) is absorbed by cold neutral hydrogen gas (HI) within galaxies,
hindering the escape of LyC photons. Since the HI reservoir of LyC emitters has
never been mapped, major uncertainties remain on how LyC photons escape
galaxies and ionize the intergalactic medium. We have directly imaged the
neutral gas in the nearby reionization-era analog galaxy Haro 11 with the 21cm
line to identify the mechanism enabling ionizing radiation escape. We find that
merger-driven interactions have caused a bulk offset of the neutral gas by
about 6 kpc from the center of the galaxy, where LyC emission production sites
are located. This could facilitate the escape of ionizing radiation into our
line of sight. Galaxy interactions can cause both elevated LyC production and
large-scale displacement of HI from the regions where these photons are
produced. They could contribute to the anisotropic escape of LyC radiation from
galaxies and the reionization of the Universe. We argue for a systematic
assessment of the effect of environment on LyC production and escape.
