JWST Reveals a Surprisingly High Fraction of Galaxies Being Spiral-like at 0.5≤ z≤4
arxiv(2023)
摘要
Spiral arms are one of the most important features used to classify the
morphology of local galaxies. The cosmic epoch when spiral arms first appeared
contains essential clues to the evolution of disk galaxies. In this letter, we
used James Webb Space Telescope (JWST) images from the Cosmic Evolution Early
Release Science Survey to visually identify spiral galaxies with redshift
0.5≤ z≤4 and stellar mass ≥10^10 M_⊙. Out of 873 galaxies,
216 were found to have a spiral structure. The spiral galaxies in our sample
have higher star formation rates (SFRs) and larger sizes than non-spiral
galaxies. We found the observed spiral fraction decreases from 48
z∼0.75 to 8
observed with the Hubble Space Telescope (HST). We even detect possible
spiral-like features at redshifts z>3. We artificially redshifted low
redshift galaxies to high redshifts and re-inspected them to evaluate
observational effects. By varying the input spiral fraction of the redshifted
sample, we found that the input fraction of ∼35
fraction at z=2-3 the best. We are able to rule out spiral fractions being
<20
fraction is surprisingly high and implies that the formation of spiral arms, as
well as disks, was earlier in the universe.
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