Resolving the Physics of Lyman Continuum Escape with HWO

[Presented at HWO25 "Towards the Habitable Worlds Observatory: Visionary Science and Transformational Technology"] 

Approximately one billion years after the Big Bang, the Universe underwent its last major phase transition, during which most of the neutral hydrogen in the intergalactic medium (IGM) was ionized. This era, known as the Epoch of Reionization (EoR), remains one of the final frontiers in cosmology. Key questions, such as the exact duration of the EoR and the nature of the astrophysical objects responsible for reionizing the Universe, are still unanswered. Measuring the output of ionizing (LyC) radiation from these objects is crucial to answering these questions. However, extinction by the IGM prevents direct observations at high redshift, which means astronomers must rely on observations of local analogs to high-redshift galaxies to understand the physics of LyC escape and how the Universe was reionized. UV spectroscopy has played a critical role, revealing the physics of stellar feedback through spectral lines. Early observations with the Hubble Space Telescope (HST) show complex relationships between LyC escape and various indicators, such as star formation surface density. There also appears to be a competition between radiation and supernova feedback as the primary mechanisms facilitating LyC escape. To fully understand the underlying physics, it is necessary to resolve galaxies down to the level of super star clusters, the primary sources of LyC photons. The advent of high-resolution multi-object/integral field unit spectroscopy with the Habitable Worlds Observatory (HWO) will be the breakthrough we need. In this talk, I will discuss recent results on the physics of LyC escape obtained with HST, outline our goals, and highlight the challenges ahead. I will also suggest various specifications for HWO, based on our work within the HWO science working groups.