Invited Presentation
The Evolution of Galaxy Morphology in the High-Redshift Universe Viewed by JWST Observations and HR5 Simulations
Presenter: Jeong Hwan Lee (Seoul National University)
The morphologies of galaxies are crucial for understanding galaxy evolution and formation over cosmic time. Prior to the advent of the James Webb Space Telescope (JWST), the morphologies of high-redshift galaxies were considered to be highly uncertain due to observational limitations. Instead, cosmological simulations such as Horizon Run 5 (HR5) have played an important role in elucidating the morphology of high-redshift galaxies. In a recent HR5 study, Park et al. (2022) suggested that the morphologies of galaxies in the cosmic morning (z>4) are dominated by disks formed in protogalactic clouds with initial angular momentum. The advent of JWST allows us to observe the morphology of high-redshift galaxies. To compare the results from observations and HR5 simulation, we study the morphologies of about 19,000 galaxies with log M*/M⊙>9 at z=0.6-8.0, using data from six JWST deep fields such as NEP-TDF, NGDEEP, CEERS, COSMOS, UDS, and SMACS J0723-7327. We classified their morphology based on their Sersic indices (n) and asymmetry (A), following the classifier used in Park et al. (2022). As presented in the HR5 study, disk morphologies are dominant for galaxies at z>4 in the low-mass regime (log M*/M⊙<11), accounting for ~70% of the total galaxy population. In contrast, in the high-mass regime (log M*/M⊙>11), the spheroid fraction tends to increase with decreasing redshift, reaching ~60% at z<1.5. This suggests that the initial disk-type morphologies in the cosmic morning have transformed into spheroid-type morphologies with mass growth over time. In conclusion, the findings from JWST data are consistent with the HR5 results, indicating the effectiveness and usefulness of cosmological simulations for predicting galaxy formation and evolution.
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