Diversity in Lyman Continuum Escape at $z\sim0.3$ Revealed by WISE Infrared Observations

Abstract

The escape of Lyman continuum (LyC) radiation from star-forming galaxies plays a key role in cosmic reionization. While strong LyC leakers are commonly identified through ultraviolet (UV) and optical diagnostics, their infrared (IR) emission remains poorly explored. We use data from the Wide-field Infrared Survey Explorer (WISE) to investigate a sample of local star-forming galaxies, which contains 20 strong LyC leakers ($S/N_\mathrm{LyC} > 3$ and $f_{\rm esc}>5\%$) and 69 non-leakers. Among the strong leakers, 8 are classified with mid-IR detections. Comparing the IR-detected and IR-undetected subsamples, we find that the IR-undetected strong leakers exhibit higher [\ion{O}{3}]5007/[\ion{O}{2}]3726,3729 (O32) ratios, bluer UV slopes, and lower metallicities than the other subsamples. In contrast, the IR-detected strong leakers show O32 ratios, UV slopes, and metallicities comparable to those of non-leakers, while maintaining a median escape fraction of $f_{\rm esc}\sim12\%$. These results indicate that significant LyC escape is not limited to galaxies with the most extreme UV and optical properties and can coexist with substantial IR emission. The Ly$α$ profiles and the morphology of the IR-detected and IR-undetected strong leakers imply that LyC photon escape in these two classes may be driven by different mechanisms. Our results highlight the diversity of LyC leakers and suggest that dusty star-forming galaxies may contribute a considerable amount to the ionizing photon budget during cosmic reionization.