The connection between the escape of ionizing radiation and galaxy properties at z ∼ 3 in the Keck Lyman continuum spectroscopic survey

The connection between the escape fraction of ionizing radiation (f(esc) ) and the properties of galaxies, such as stellar mass (M*), age, star-formation rate (SFR), and dust content, are key inputs for reionization models, but many of these relationships remain untested at high redshift. We present an analysis of a sample of 96 z similar to 3 galaxies from the Keck Lyman Continuum Spectroscopic Survey (KLCS). These galaxies have both sensitive Keck/LRIS spectroscopic measurements of the Lyman continuum (LyC) region, and multiband photometry that places constraints on stellar population parameters. We construct composite spectra from subsamples binned as a function of galaxy property and quantify the ionizing-photon escape for each composite. We find a significant anti-correlation between f(esc) and M-*, consistent with predictions from cosmological zoom-in simulations. We also find significant anti-correlation between f(esc) and E(B-V), encoding the underlying physics of LyC escape in our sample. We also find no significant correlation between f(esc) and either stellar age or specific SFR (= SFR/M-*), challenging interpretations that synchronize recent star formation and favorable conditions for ionizing escape. The galaxy properties now shown to correlate with f(esc) in the KLCS are Ly alpha equivalent width, UV Luminosity, M-*, SFR, and E(B-V), but not age or sSFR. This comprehensive analysis of galaxy properties and LyC escape at high redshift will be used to guide future models and observations of the reionization epoch.

Automated summary

A study found that there is a correlation between the escape fraction of ionizing radiation (f(esc)) and properties of galaxies such as stellar mass (M*), age, star-formation rate (SFR), and dust content, which are important for reionization models. An analysis of 96 z≈3 galaxies showed that there is a significant anti-correlation between f(esc) and M-*, as well as between f(esc) and E(B-V). However, there is no significant correlation between f(esc) and either stellar age or specific SFR, challenging previous interpretations.