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

T. Treu, A. Calabro, M. Castellano, N. Leethochawalit, E. Merlin, A. Fontana, L. Yang, T. Morishita, M. Trenti, A. Dressler, C. Mason, D. Paris, L. Pentericci, G. Roberts-Borsani, B. Vulcani, K. Boyett, M. Bradac, K. Glazebrook, T. Jones, D. Marchesini, S. Mascia, T. Nanayakkara, P. Santini, V. Strait, E. Vanzella, X. Wang

Published 2022-07-27Version 1

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 7-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 Lyman $\alpha$ and 6000-4000\AA, 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 4/21 galaxies. Our results are consistent with a scenario in which Lyman Break galaxies -- observed when the universe is only 400-800 Myrs old - are growing via a combination of rapid galaxy-scale star formation supplemented by accretion of star forming clumps and interactions.