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Arxiv: JWST Reveals a Surprisingly High Fraction of Galaxies Being Spiral-like at 0.5\leq z\leq4 Published: 12/19/2023 8:20:34 PM Updated: 4/23/2024 5:58:11 PM

Paper abstract: Spiral arms are one of the most important features used to classify themorphology of local galaxies. The cosmic epoch when spiral arms first appearedcontains essential clues to the evolution of disk galaxies. In this letter, weused James Webb Space Telescope (JWST) images from the Cosmic Evolution EarlyRelease Science Survey to visually identify spiral galaxies with redshift0.5<= z<=4 and stellar mass >=10^{10}\; M_\odot. Out of 873 galaxies,216 were found to have a spiral structure. The spiral galaxies in our samplehave higher star formation rates (SFRs) and larger sizes than non-spiralgalaxies. We found the observed spiral fraction decreases from 48% atz~0.75 to 8% at z~2.75. These fractions are higher than the fractionsobserved with the Hubble Space Telescope (HST). We even detect possiblespiral-like features at redshifts z>3. We artificially redshifted lowredshift galaxies to high redshifts and re-inspected them to evaluateobservational effects. By varying the input spiral fraction of the redshiftedsample, we found that the input fraction of ~35% matches the observedfraction at z=2-3 the best. We are able to rule out spiral fractions being<20% (2\sigma) and <10% (3\sigma) for real galaxies at z~3. Thisfraction is surprisingly high and implies that the formation of spiral arms, aswell as disks, was earlier in the universe.