Direct detection of ionizing radiation with Habitable Worlds Observatory

Requirements for the direct detection of ionizing radiation escaping from galaxies by the Habitable Worlds Observatory are reviewed along with an outline of the sampling statistics required to create Lyman continuum (LyC) luminosity functions over the redshift interval from 0.2<z<1.2. The goal is to determine how the shape of the escaping LyC evolves with redshift and assess its impact on creating and sustaining the metagalactic ionizing background (MIB). A robust program that can deliver samples ∼500 objects per Δz=0.2 redshift interval and detect LyC escape fractions f900e<1% for sub-L900(1+z)* galaxies requires a spectral multiplexing capability with sensitivity to ≳30 abmag. A short wavelength cutoff of ∼1000 Å will allow the first measurements of the LyC spectral energy distribution down to a rest frame cutoff from 830≲λcutoffLyC≲450 Å over the proposed redshift interval, allowing for a more complete assessment of the ionizing radiation escaping into the MIB.