EUROPEAN SPACE AGENCY

Connecting Lyα and Ionizing Photon Escape in the Sunburst Arc

DOI: 10.3847/1538-4357/ad9247 Bibcode: 2024ApJ...977..234O

Hutchison, Taylor A.; Mahler, Guillaume; Chisholm, John; Rigby, Jane R.; Florian, Michael; Sharon, Keren; Dahle, Håkon; Kim, Keunho J.; Navarre, Alexander; Bayliss, Matthew B.; Gladders, Michael D.; Khullar, Gourav; Rivera-Thorsen, T. Emil; Welch, Brian; Owens, M. Riley; Burns, Jessica G.; Malhas, Christopher M.; Gassis, Raven; Choe, Suhyeon; Adhikari, Prasanna

United States, Sweden, United Kingdom, Norway

Abstract

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 ( ) 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 , 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.

2024 • The Astrophysical Journal
eHST 3
Back to Publications