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arXiv · 2606.26355

Probing the Nature of Lyman Continuum Emitting and Low-metallicity Galaxies Using the SKA

Omkar Bait·Daniel Schaerer·Mark Sargent
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Abstract

The sources responsible for cosmic reionization remain a key open question in observational cosmology. Recent JWST results increasingly suggest that low-mass star-forming galaxies (e.g., compact starbursts and strong emission-line systems) dominated the ionizing photon budget. The physical mechanisms driving Lyman continuum (LyC) photon escape, including supernova, radiative, and cosmic-ray feedback, and the origin of extreme ionization conditions, remain poorly understood. Radio continuum (RC) emission, a well-established star-formation tracer in normal galaxies, is not yet well characterized in such extreme systems, which exhibit high star-formation rate densities, young stellar populations, low metallicity, and hard ionizing spectra. Targeted mid-frequency ($1-15$,GHz) observations with SKA precursors have begun probing low-redshift LyC emitters (LCEs), revealing links between RC spectral index, LyC escape fraction, ionization conditions, metallicity, and SFR surface density, alongwith deviations from the canonical RC$-$SFR relation. The higher sensitivity of the SKA Array Assemblies across Bands $\sim 1-5$ will enable systematic studies of fainter LCEs and low-mass, metal-poor galaxies. We present number density predictions for LCE candidates at $z \sim 1$-$3$, showing that SKA-Mid surveys can assemble samples of $\sim10-100$ candidates per square degree over a star-formation rate range of $1-100$,$M_{\odot}$yr$^{-1}$, making a dedicated SKA Large Programme scientifically feasible. With the full SKA, in synergy with JWST and next generation telescopes, multi-wavelength analyses will robustly constrain the thermal and non-thermal RC components and cosmic-ray energy spectra, providing critical insights into the feedback processes governing LyC escape and star formation in the early universe.

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Omkar Bait, Daniel Schaerer, Mark Sargent. 2026-06-24. Probing the Nature of Lyman Continuum Emitting and Low-metallicity Galaxies Using the SKA. https://arxiv.org/abs/2606.26355

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