Description
In its first few years of operation, the James Webb Space Telescope (JWST) has revolutionised our understanding of galaxy formation in the early Universe. For the first time, its unprecedented sensitivity and spatial resolution have enabled direct constraints on the kinematics of ionised gas during the Epoch of Reionisation. Through NIRSpec IFU and MOS observations, along with NIRCam WFSS data, JWST has provided detailed measurements of the ionised gas dynamics, offering new insights into the internal motions of high-redshift galaxies. These observations, when combined with state-of-the-art cosmological simulations, are allowing the extragalactic astronomy community to make significant advances in characterising the first generation of galaxies and testing the current cosmological framework.
To interpret these observations, we use the THESAN-zoom simulations—a suite of high-resolution, zoom-in radiation-hydrodynamic simulations. These simulations preserve the realistic reionisation history of the parent simulation while incorporating updated stellar feedback and multi-phase interstellar medium physics, making them an ideal theoretical counterpart to JWST’s observational efforts. By analysing the kinematics of stars, dark matter, and gas (across cold, warm, and hot phases), as well as the H-alpha emitting ionised gas, we examine key properties such as rotational velocity, velocity dispersion, circularity, and spin. This comprehensive kinematic analysis provides new constraints on the rotational support and feedback processes in early galaxies, which are critical for estimating their stellar masses and understanding their dynamical evolution during the Epoch of Reionisation.