Little impact of mergers and galaxy morphology on the production and escape of ionizing photons in the early Universe
Sara Mascia, L. Pentericci, Mario Llerena, A. Calabrò, J. Matthee, S. Flury, Fabio Pacucci, A. Jaskot, R. Amorín, Rachana Bhatawdekar, M Castellano, N. J. Cleri, Luca Costantin, Kelcey Davis, Claudia Di Cesare, M. Dickinson, A. Fontana, Yuchen Guo, M. Giavalisco, Benne W. Holwerda, Weida Hu, Intae Jung, Jeyhan S. Kartaltepe, Daichi Kashino, A. M. Koekemoer, R. A. Lucas, Jeffrey M. Lotz, Lorenzo Napolitano, Shardha Jogee, Stephen M. Wilkins
Abstract
Compact, star-forming galaxies with high star formation rate surface densities (Σ SFR ) are often efficient Lyman continuum (LyC) emitters at z ≤ 4.5, likely because intense stellar feedback creates low-density channels that allow photons to escape. Irregular or disturbed morphologies, such as those resulting from mergers, can also facilitate LyC escape by creating anisotropic gas distributions. We investigated the influence of galaxy morphology on LyC production and escape at redshifts 5 ≤ z ≤ 7 using observations from various James Webb Space Telescope (JWST) surveys. Our sample consists of 436 sources, which are predominantly low-mass (∼10 8.15 M ⊙ ), star-forming galaxies with ionizing photon efficiency ( ξ ion ) values consistent with canonical expectations. Since direct measurements of f esc are not possible during the Epoch of Reionization (EoR), we predicted f esc for high-redshift galaxies by applying survival analysis to a subsample of LyC emitters from the Low-Redshift Lyman Continuum Survey (LzLCS), selected to be direct analogs of reionization-era galaxies. We find that these galaxies exhibit, on average, modest predicted escape fractions (∼0.04). In addition, we evaluated the correlation between morphological features and LyC emission. Our findings indicate that neither ξ ion nor the predicted f esc values show a significant correlation with the presence of merger signatures. This suggests that in low-mass galaxies at z ≥ 5, strong morphological disturbances are not the primary mechanism driving LyC emission and leakage. Instead, compactness and star formation activity likely play a more pivotal role in regulating LyC escape.