2022MNRAS.516.2062P

The connection between the escape fraction of ionizing photons (f_esc) and star formation rate surface density (Σ_SFR) is a key input for reionization models, but remains untested at high redshift. We analyse 35 z ∼ 3 galaxies from the Keck Lyman Continuum Survey (KLCS) covered by deep, rest far-UV spectra of the Lyman continuum (LyC) and high-resolution HST V₆₀₆ imaging, enabling estimates of both f_esc and rest-UV sizes. Using Sérsic profile fits to HST images and spectral-energy distribution fits to multiband photometry, we measure effective sizes and SFRs for the galaxies in our sample, and separate the sample into two bins of Σ_SFR. Based on composite spectra, we estimate 〈f_esc〉 for both Σ_SFR subsamples, finding no significant difference in 〈f_esc〉 between the two. To test the representativeness of the KLCS HST sample and robustness of this result, we attempt to recover the well-established correlation between f_esc and Lyα equivalent width. This correlation is not significant within the KLCS HST sample, indicating that the sample is insufficient for correlating f_esc and galaxy properties such as Σ_SFR. We perform stacking simulations using the KLCS parent sample to determine the optimal sample size for robust probes of the f_esc-Σ_SFR connection to inform future observing programs. For a program with a selection independent of ionizing properties, ≥90 objects are required; for one preferentially observing strongly-leaking LyC sources, ≥58 objects are required. More generally, measuring the connection between f_esc and Σ_SFR requires a larger, representative sample spanning a wide dynamic range in galaxies properties such as Σ_SFR.