CEERS Key Paper. III. The Diversity of Galaxy Structure and Morphology at z = 3–9 with JWST

CEERS, Swara Ravindranath, Raymond C. Simons, Gregory F Snyder, Rachel S. Somerville, Elizabeth Stanway, Amber N. Straughn, Sandro Tacchella, Jonathan R. Trump, Jesús Vega-Ferrero, Stephen Wilkins, Guang Yang, Jorge A. Zavala

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Abstract

We present a comprehensive analysis of the evolution of the morphological and structural properties of a large sample of galaxies at z = 3-9 using early James Webb Space Telescope (JWST) CEERS NIRCam observations. Our sample consists of 850 galaxies at z > 3 detected in both Hubble Space Telescope (HST)/WFC3 and CEERS JWST/NIRCam images, enabling a comparison of HST and JWST morphologies. We conduct a set of visual classifications, with each galaxy in the sample classified three times. We also measure quantitative morphologies across all NIRCam filters. We find that galaxies at z > 3 have a wide diversity of morphologies. Galaxies with disks make up 60% of galaxies at z = 3, and this fraction drops to ∼30% at z = 6-9, while galaxies with spheroids make up ∼30%-40% across the redshift range, and pure spheroids with no evidence for disks or irregular features make up ∼20%. The fraction of galaxies with irregular features is roughly constant at all redshifts (∼40%-50%), while those that are purely irregular increases from ∼12% to ∼20% at z > 4.5. We note that these are apparent fractions, as many observational effects impact the visibility of morphological features at high redshift. On average, Spheroid-only galaxies have a higher Sérsic index, smaller size, and higher axis ratio than disk or irregular galaxies. Across all redshifts, smaller spheroid and disk galaxies tend to be rounder. Overall, these trends suggest that galaxies with established disks and spheroids exist across the full redshift range of this study, and further work with large samples at higher redshift is needed to quantify when these features first formed.

Original languageEnglish
Article numberL15
Number of pages17
JournalThe Astrophysical Journal Letters
Volume946
Issue number1
DOIs
Publication statusPublished - 27 Mar 2023

Bibliographical note

Funding Information:
Support for this work was provided by NASA through grants JWST-ERS-01345.015-A and HST-AR-15802.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5–26555. This research is based in part on observations made with the NASA/ESA Hubble Space Telescope obtained from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 526555. J.S.K. would like to acknowledge the important contributions of her cats, T’Pol and Shran, who diligently attended every telecon and assisted in paper editing.

Some of the data presented in this paper are available at the Mikulski Archive for Space Telescopes (MAST) at the Space Telescope Science Institute. The specific observations can be accessed via doi:10.17909/qhb4-fy92 and doi:10.17909/ T94S3X.

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