Connecting Lyα and Ionizing Photon Escape in the Sunburst Arc

We investigate the Lyα and Lyman continuum (LyC) properties of the Sunburst Arc, a z = 2.37 gravitationally lensed galaxy with a multiply imaged, compact region leaking LyC and a triple-peaked Lyα profile indicating direct Lyα escape. Non-LyC-leaking regions show a redshifted Lyα peak, a redshifted and central Lyα peak, or a triple-peaked Lyα profile. We measure the properties of the Lyα profile from different regions of the galaxy using R ∼ 5000 Magellan/Magellan Echellette spectra. We compare the Lyα spectral properties to LyC and narrowband Lyα maps from Hubble Space Telescope imaging to explore the subgalactic Lyα−LyC connection. We find strong correlations (Pearson correlation coefficient r > 0.6) between the LyC escape fraction ( \(f_{esc}^{LyC}\)) and Lyα (1) peak separation \(v_{sep}\), (2) ratio of the minimum flux density between the redshifted and blueshifted Lyα peaks to continuum flux density \(\frac{f_{min}}{f_{cont}}\), and (3) equivalent width. We favor a complex H I geometry to explain the Lyα profiles from non-LyC-leaking regions and suggest two H I geometries that could diffuse and/or rescatter the central Lyα peak from the LyC-leaking region into our sight line across transverse distances of several hundred parsecs. Our results emphasize the complexity of Lyα radiative transfer and its sensitivity to the anisotropies of H I gas on subgalactic scales. Large differences in the physical scales on which we observe spatially variable direct- escape Lyα, blueshifted Lyα, and escaping LyC photons in the Sunburst Arc underscore the importance of resolving the physical scales that govern Lyα and LyC escape.

Recommended citation: Owens, M. R., Kim, K. J., Bayliss, M. B., Rivera-Thorsen, T. E., Sharon, K., Rigby, J. R., Navarre, A., Florian, M., Gladders, M. D., Burns, J. G., Khullar, G., Chisholm, J., Mahler, G., Dahle, H., Malhas, C. M., Welch, B., Hutchison, T. A., Gassis, R., Choe, S., & Adhikari, P. (2024). Connecting Ly\ensuremathα and Ionizing Photon Escape in the Sunburst Arc. \apj, 977(2), e234. https://doi.org/10.3847/1538-4357/ad9247
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