EPOCHS. XI. The Structure and Morphology of Galaxies in the Epoch of Reionization to <i>z</i> ∼ 12.5

Abstract We present a structural analysis of 520 galaxy candidates at 6.5 &lt; z &lt; 12.5 with a signal-to-noise ratio of &gt;10 σ in the F444W filter taken from the EPOCHS v1 sample, consisting of uniformly reduced deep JWST NIRCam data covering the CEERS, JADES GOODS-S, NGDEEP, SMACS-0723, GLASS, and PEARLS surveys. We use standard software to fit single Sérsic models to each galaxy in the rest-frame optical and extract their parametric structural parameters (Sérsic index, half-light radius, and axis ratio) and Morfometryka to measure their nonparametric concentration and asymmetry parameters. We find a wide range of sizes for these early galaxies, with galaxy sizes overall continuing to become progressively smaller in the high-redshift regime, following <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>R</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>e</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mfenced close=")" open="("> <mml:mrow> <mml:mn>2.12</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.28</mml:mn> </mml:mrow> </mml:mfenced> <mml:msup> <mml:mrow> <mml:mfenced close=")" open="("> <mml:mrow> <mml:mn>1</mml:mn> <mml:mo>+</mml:mo> <mml:mi>z</mml:mi> </mml:mrow> </mml:mfenced> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.67</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.06</mml:mn> </mml:mrow> </mml:msup> </mml:math> kpc. We further find a galaxy size–mass correlation up to z ∼ 12, with galaxies of a given mass also becoming smaller. Using nonparametric methods, we find that galaxy merger fractions, classified through asymmetry parameters, at these redshifts remain consistent with those in the literature, maintaining a value of f m ∼ 0.12 ± 0.07 showing little dependence with redshift when combined with the literature at z &gt; 4. We find that galaxies that are smaller in size also appear rounder, with an excess of high axis ratio objects. Finally, we artificially redshift a subsample of our objects to determine how robust the observational trends we see are, determining that the observed trends are due to real evolutionary effects, rather than being a consequence of redshift effects.

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Publication Details

Journal
The Astrophysical Journal
Published
2025-04-14
DOI
https://doi.org/10.3847/1538-4357/adb968
Citations
11
Primary Topic
Galaxies: Formation, Evolution, Phenomena
Type
article
Field-Weighted Citation Impact
12.70

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article

EPOCHS. XI. The Structure and Morphology of Galaxies in the Epoch of Reionization to z ∼ 12.5

Jake Summers, Vadim Rusakov, Rogier A. Windhorst, Rolf A. Jansen et al.
11 citations
The Astrophysical Journal
Galaxies: Formation, Evolution, Phenomena
12.70
article

EPOCHS. XI. The Structure and Morphology of Galaxies in the Epoch of Reionization to z ∼ 12.5

Jake Summers, Vadim Rusakov, Rogier A. Windhorst, Rolf A. Jansen, Tom Broadhurst, Norman A. Grogin, Nimish P. Hathi, Nathan Adams, Russell E. Ryan, Madeline A. Marshall, Thomas Harvey, Christopher J. Conselice, Seth H. Cohen, Anton M. Koekemoer, Dan Coe, Jordan C. J. D’Silva, Simon P. Driver, Haojing Yan, Brenda Frye, James Trussler, Nor Pirzkal, Duncan Austin, Fabrício Ferrari, Christopher N. A. Willmer, A. S. G. Robotham, Lewi Westcott, Qiong Li, Leonardo Ferreira, Rafael Ortiz, Qiao Duan, Honor Harris, Caio Goolsby
article en
11 citations

Abstract

Abstract We present a structural analysis of 520 galaxy candidates at 6.5 &lt; z &lt; 12.5 with a signal-to-noise ratio of &gt;10 σ in the F444W filter taken from the EPOCHS v1 sample, consisting of uniformly reduced deep JWST NIRCam data covering the CEERS, JADES GOODS-S, NGDEEP, SMACS-0723, GLASS, and PEARLS surveys. We use standard software to fit single Sérsic models to each galaxy in the rest-frame optical and extract their parametric structural parameters (Sérsic index, half-light radius, and axis ratio) and Morfometryka to measure their nonparametric concentration and asymmetry parameters. We find a wide range of sizes for these early galaxies, with galaxy sizes overall continuing to become progressively smaller in the high-redshift regime, following <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>R</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>e</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mfenced close=")" open="("> <mml:mrow> <mml:mn>2.12</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.28</mml:mn> </mml:mrow> </mml:mfenced> <mml:msup> <mml:mrow> <mml:mfenced close=")" open="("> <mml:mrow> <mml:mn>1</mml:mn> <mml:mo>+</mml:mo> <mml:mi>z</mml:mi> </mml:mrow> </mml:mfenced> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.67</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.06</mml:mn> </mml:mrow> </mml:msup> </mml:math> kpc. We further find a galaxy size–mass correlation up to z ∼ 12, with galaxies of a given mass also becoming smaller. Using nonparametric methods, we find that galaxy merger fractions, classified through asymmetry parameters, at these redshifts remain consistent with those in the literature, maintaining a value of f m ∼ 0.12 ± 0.07 showing little dependence with redshift when combined with the literature at z &gt; 4. We find that galaxies that are smaller in size also appear rounder, with an excess of high axis ratio objects. Finally, we artificially redshift a subsample of our objects to determine how robust the observational trends we see are, determining that the observed trends are due to real evolutionary effects, rather than being a consequence of redshift effects.

The Astrophysical JournalVol. 983(2)
Ikerbasque (ES), Universidade Federal do Rio Grande (BR), Space Telescope Science Institute (US), Los Alamos National Laboratory (US), University of Arizona (US), Johns Hopkins University (US), University of the Basque Country (ES), The University of Western Australia (AU), University of Victoria (CA), University of Manchester (GB), ASTRO-3D (AU), Université Bourgogne Franche-Comté (FR), ARC Centre of Excellence for All-sky Astrophysics (AU), International Centre for Radio Astronomy Research (AU), Arizona State University (US), University of Missouri (US)
National Aeronautics and Space Administration, Space Telescope Science Institute, University of Manchester, Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, Nuclear Safety and Security Commission, Goddard Space Flight Center, Science and Technology Facilities Council
Openalex Percentile: Top 1%
Galaxies: Formation, Evolution, Phenomena
12.70
DOIOpen Access PDFOpenAlex
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