Morphology of Galaxies in JWST Fields: Initial Distribution and Evolution of Galaxy Morphology

초록

A recent study from the Horizon Run 5 (HR5) cosmological simulation has predicted that galaxies with log M * / M (circle dot) less than or similar to 10 in the cosmic morning (10 greater than or similar to z greater than or similar to 4) dominantly have disk-like morphology in the Lambda CDM universe, which is driven by the tidal torque in the initial fluctuations of matter. For a direct comparison with observation we identify a total of about 19,000 James Webb Space Telescope (JWST) galaxies with log M * / M (circle dot) > 9 at z = 0.6-8.0 utilizing deep JWST/NIRCam images of publicly released fields, including North Ecliptic Pole Time-Domain Fields, Next Generation Deep Extragalactic Exploratory Public survey, Cosmic Evolution Early Release Science Survey, Cosmic Evolution Survey, UltraDeep Survey, and SMACS J0723-7327. We estimate their stellar masses and photometric redshifts with the redshift dispersion of sigma NMAD = 0.009 and an outlier fraction of only about 6%. We classify galaxies into three morphological types, disks, spheroids, and irregulars, applying the same criteria used in the HR5 study. The morphological distribution of the JWST galaxies shows that disk galaxies account for 60%-70% at all redshift ranges. However, in the high-mass regime ( log M * / M (circle dot) greater than or similar to 11 ), spheroidal morphology becomes the dominant type. This implies that the mass growth of galaxies is accompanied by a morphological transition from disks to spheroids. The fraction of irregulars is about 20% or less at all masses and redshifts. All the trends in the morphology distribution are consistently found in the six JWST fields. These results are in close agreement with the results from the HR5 simulation, particularly confirming the prevalence of disk galaxies at small masses in the cosmic morning and noon.

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