COSMOS-Web: Unraveling the Evolution of Galaxy Size and Related Properties at 2 < <i>z</i> < 10
Abstract We measure galaxy sizes from 2 < z < 10 using COSMOS-Web, the largest-area JWST imaging survey to date, covering ∼0.54 deg 2 . We analyze the rest-frame optical (∼5000 Å) size evolution and its scaling relation with stellar mass ( <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:msubsup> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>*</mml:mo> </mml:mrow> <mml:mrow> <mml:mi>α</mml:mi> </mml:mrow> </mml:msubsup> </mml:math> ) for star-forming and quiescent galaxies. For star-forming galaxies, the slope α remains approximately 0.20 at 2 < z < 8, showing no significant evolution over this redshift range. At higher redshifts, the slopes are −0.13 ± 0.15 and 0.37 ± 0.36 for 8 < z < 9 and 9 < z < 10, respectively. At fixed galaxy mass, the size evolution for star-forming galaxies follows R e ∝ (1 + z ) −1.21±0.05 . For quiescent galaxies, the size–mass relation is steeper with α ∼ 0.5–0.8 at 2 < z < 5, and size evolves as R e ∝ (1 + z ) −0.81±0.26 . We find that the size−mass relation is consistent between UV and optical at z < 8 for star-forming galaxies. However, we observe a decrease in the slope from UV to optical at z > 8, with a tentative negative slope in the optical at 8 < z < 9, suggesting a complex interplay between intrinsic galaxy properties and observational effects such as dust attenuation. We discuss the ratio between galaxies’ half-light radius and underlying halos’ virial radius, R vir , and find the median value of R e / R vir = 2.7%. The star formation rate surface density evolves as <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">Σ</mml:mi> </mml:mrow> <mml:mrow> <mml:mspace width="0.1em"/> <mml:mtext>SFR</mml:mtext> <mml:mspace width="0.1em"/> </mml:mrow> </mml:msub> <mml:mo>/</mml:mo> <mml:mo stretchy="false">(</mml:mo> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> <mml:mo>/</mml:mo> <mml:mi mathvariant="normal">yr</mml:mi> <mml:mo>/</mml:mo> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">kpc</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> <mml:mo stretchy="false">)</mml:mo> <mml:mo stretchy="false">)</mml:mo> <mml:mo>=</mml:mo> </mml:math> (0.20 ± 0.08) z + (−0.65 ± 0.51), and the Σ SFR – M * relation remains flat at 2 < z < 10. Lastly, we identify a threshold in stellar mass surface density <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">Σ</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>e</mml:mi> </mml:mrow> </mml:msub> <mml:mo>/</mml:mo> <mml:mo stretchy="false">(</mml:mo> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> <mml:mo>/</mml:mo> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">kpc</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> <mml:mo stretchy="false">)</mml:mo> <mml:mo stretchy="false">)</mml:mo> <mml:mo>∼</mml:mo> <mml:mn>9.5</mml:mn> <mml:mo>−</mml:mo> <mml:mn>10</mml:mn> </mml:math> marking the transition to compact, quenched galaxies from extended, star-forming progenitors. In summary, our findings show that the extensive COSMOS-Web dataset at z > 3 provides new insights into galaxy size and related properties in the rest-frame optical.
Authors
- Louise Paquereau (ORCID: https://orcid.org/0000-0003-2397-0360)
- Xuheng Ding (ORCID: https://orcid.org/0000-0001-8917-2148)
- Si-Yue Yu (ORCID: https://orcid.org/0000-0002-3462-4175)
- Lilan Yang (ORCID: https://orcid.org/0000-0002-8434-880X)
- Marko Shuntov (ORCID: https://orcid.org/0000-0002-7087-0701)
- Hollis B. Akins (ORCID: https://orcid.org/0000-0003-3596-8794)
- G. Gozaliasl (ORCID: https://orcid.org/0000-0002-0236-919X)
- Shuowen Jin
- J. D. Silverman (ORCID: https://orcid.org/0000-0002-0000-6977)
- R. Massey (ORCID: https://orcid.org/0000-0002-6085-3780)
- H. J. McCracken (ORCID: https://orcid.org/0000-0002-9489-7765)
- Nicole E. Drakos (ORCID: https://orcid.org/0000-0003-4761-2197)
- Anton M. Koekemoer (ORCID: https://orcid.org/0000-0002-6610-2048)
- Caitlin M. Casey (ORCID: https://orcid.org/0000-0002-0930-6466)
- O. Ilbert (ORCID: https://orcid.org/0000-0002-7303-4397)
- G. Magdis (ORCID: https://orcid.org/0000-0002-4872-2294)
- Maximilien Franco (ORCID: https://orcid.org/0000-0002-3560-8599)
- Jason Rhodes (ORCID: https://orcid.org/0000-0002-4485-8549)
- Brant E. Robertson (ORCID: https://orcid.org/0000-0002-4271-0364)
- Steven Gillman (ORCID: https://orcid.org/0000-0001-9885-4589)
- Sune Toft (ORCID: https://orcid.org/0000-0003-3631-7176)
- Rafael C. Arango-Toro (ORCID: https://orcid.org/0000-0002-0569-5222)
- Jeyhan S. Kartaltepe (ORCID: https://orcid.org/0000-0001-9187-3605)
- Daizhong Liu (ORCID: https://orcid.org/0000-0001-9773-7479)
- Takumi S. Tanaka (ORCID: https://orcid.org/0009-0003-4742-7060)
- Andreas L. Faisst (ORCID: https://orcid.org/0000-0002-9382-9832)
- Natalie Allen (ORCID: https://orcid.org/0000-0001-9610-7950)
- Mark J. Achenbach (ORCID: https://orcid.org/0009-0000-7385-3539)
Institutions
- University of Hawaiʻi at Mānoa (US)
- California Institute of Technology (US)
- University of Copenhagen (DK)
- Centre National de la Recherche Scientifique (FR)
- Space Telescope Science Institute (US)
- Jet Propulsion Laboratory (US)
- University of Helsinki (FI)
- University of California, Santa Barbara (US)
- Rochester Institute of Technology (US)
- Universidad de La Laguna (ES)
- Kavli Institute for the Physics and Mathematics of the Universe (JP)
- University of California, Santa Cruz (US)
- Durham University (GB)
- Chinese Academy of Sciences (CN)
- Université Paris Cité (FR)
- Aix-Marseille Université (FR)
- Commissariat à l'Énergie Atomique et aux Énergies Alternatives (FR)
- Université Paris Sciences et Lettres (FR)
- Université Paris-Saclay (FR)
- Observatoire de Paris (FR)
- Institut d'Astrophysique de Paris (FR)
- Purple Mountain Observatory (CN)
- University of Hawaii at Hilo (US)
- Wuhan University (CN)
- Sorbonne Université (FR)
- Astrophysique, Instrumentation et Modélisation (FR)
- Université Bourgogne Franche-Comté (FR)
- CEA Paris-Saclay (FR)
- Instituto de Astrofísica de Canarias (ES)
- Infrared Processing and Analysis Center (US)
- The University of Tokyo (JP)
- The University of Texas at Austin (US)
- Technical University of Denmark (DK)
- Aalto University (FI)
Publication Details
- Journal
- The Astrophysical Journal Supplement Series
- Published
- 2025-12-01
- DOI
- https://doi.org/10.3847/1538-4365/ae0e1b
- Citations
- 7
- Primary Topic
- Galaxies: Formation, Evolution, Phenomena
- Type
- article
- Field-Weighted Citation Impact
- 8.08