Early Results From GLASS-JWST. XII. The Morphology of Galaxies at the Epoch of Reionization

Star-forming galaxies can exhibit strong morphological differences between the rest-frame far-UV and optical, reflecting inhomogeneities in star formation and dust attenuation. We exploit deep, high-resolution, NIRCAM seven-band observations to take a first look at the morphology of galaxies in the epoch of reionization (z > 7), and its variation in the rest-frame wavelength range between Ly alpha and 6000-4000 angstrom, at z = 7-12. We find no dramatic variations in morphology with wavelength-of the kind that would have overturned anything we have learned from the Hubble Space Telescope. No significant trends between morphology and wavelengths are detected using standard quantitative morphology statistics. We detect signatures of mergers/interactions in 4/19 galaxies. Our results are consistent with a scenario in which Lyman-break galaxies-observed when the universe is only 400-800 Myr old-are growing via a combination of rapid, galaxy-scale star formation supplemented by the accretion of star-forming clumps and interactions.

Automated summary

Using deep, high-resolution NIRCAM observations, we study the morphology of galaxies during the epoch of reionization and its variation in the rest-frame wavelength range. We find no significant variations in morphology with wavelength and detect signatures of mergers/interactions in a fraction of galaxies. These results suggest that Lyman-break galaxies grow through rapid, galaxy-scale star formation accompanied by the accretion of star-forming clumps and interactions.