We observed the gravitationally lensed (μ=9.6±0.19) galaxy A1689-zD1 at z=7.1 in bands 3, 6, and 8 of the Atacama Large Millimeter/submillimeter Array. These high-resolution observations (≈200 pc) enabled us to separate the source into five components in the [CII] 158μm and [OIII] 88mum emission lines within a projected distance of 2 kpc. Even though these components appear to vary strongly from one another in both their line, continuum, and optical characteristics, the assembly of components do not show ordered rotation and appear consistent with simulations of a galaxy system undergoing the process of assembly. The total dynamical mass of the galaxy (2×1010 M⊙) is an order of magnitude larger than the spectrally estimated stellar mass, suggesting a near-complete optical obscuration of the bulk of the stellar component. Comparing the line ratios as well as the line properties to other properties such as the star formation rate, we find that A1689-zD1 is consistent with the relations derived from local star-forming galaxies. Even though A1689-zD1 lies on local star formation scaling relations and has a high dust and stellar mass estimate, the kinematics suggest it is in an early assembly stage, which could lead to it becoming a disk galaxy at a later stage.
@article{arxiv.2509.19475,
title = {Early galaxy evolution: The complex interstellar medium distribution of the z~7 galaxy A1689-zD1},
author = {Kirsten K. Knudsen and Darach Watson and Johan Richard and David T. Frayer and Seiji Fujimoto and Hollis Akins and Tom Bakx and Nina Bonaventura and Gabriel Brammer and Lise Christensen and Takuya Hashimoto and Akio K. Inoue and Hiroshi Matsuo and Michał J. Michałowski and Jorge A. Zavala},
journal= {arXiv preprint arXiv:2509.19475},
year = {2025}
}