Tracing Lyman alpha escape in the CRISTAL-02 galaxy at z~5.3

Abstract

Aim. We investigate the mechanisms regulating Lyman-alpha (Ly-a) escape in the star-forming galaxy CRISTAL-02 at z~5.3. The galaxy hosts five distinct clumps, with Clumps A and B suggested as potential active galactic nuclei (AGN) candidates. We study how AGN or star formation activity influences the spatial distribution and escape of Ly-a emission. Methods. Using VLT/MUSE Ly-a and JWST/NIRSpec IFU H-a and H-b observations, complemented by NIRCam UV imaging, we constructed spatially matched emission-line maps. We derived flux, line-ratio, and extinction maps, together with spatially resolved Ly-a escape fractions and ionizing photon production efficiencies. Results. Ly-a emission extends preferentially along the [C ii] outflow direction, while H-a and UV trace the galactic disk. Clumps A and B show contrasting properties: Clump A, with lower dust attenuation, exhibits enhanced Ly-a/H-a ratios and a higher Ly-a escape fraction, whereas Clump B shows stronger H-a and UV emission but suppressed Ly-a. These results suggest that Ly-a escape is influenced by outflows, dust attenuation, and local gas conditions. Conclusions. We present spatially resolved measurements of the Ly-a escape fraction and ionizing photon production efficiency in a galaxy at z~5.3, highlighting the role of feedback-driven gas clearing and anisotropic outflows in shaping Ly-a emission. The evidence favors an outflow, but the available data cannot uniquely distinguish between AGN- and star formation-driven feedback. Future spatially resolved Ly-a, H-a, and [C ii] observations will be crucial for identifying the dominant feedback mechanism.