COSMOS-Web: Galaxy Size and Surface Brightness Evolution at Rest-Frame 1.22 $μ$m Since $z=3$
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| Format: | Preprint |
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2026
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| _version_ | 1866918531699834880 |
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| author | Yu, Si-Yue Faisst, Andreas L. Fang, Taotao Toni, Greta Moscardini, Lauro Franco, Maximilien Samir, Rasha M. Hirschmann, Michaela Zhang, Xiaoxia Leroy, Gavin |
| author_facet | Yu, Si-Yue Faisst, Andreas L. Fang, Taotao Toni, Greta Moscardini, Lauro Franco, Maximilien Samir, Rasha M. Hirschmann, Michaela Zhang, Xiaoxia Leroy, Gavin |
| contents | We present the evolution of galaxy size and surface brightness in the rest-frame $J$ band (1.22 $μ$m), tracing the stellar mass distribution, over $0.5 \leq z \leq 3$, using a sample of 15,420 galaxies with stellar masses $M_\star=10^{10}$-$10^{11.5}\ M_{\odot}$ from the JWST COSMOS-Web survey. The rest-frame $J$-band effective radius ($R_{e,J}$) is obtained from previous measurements and mapped from the available JWST/NIRCam filters, while the surface brightness ($μ_J$) is corrected for dust extinction and cosmological dimming. At a characteristic mass of $M_\star = 5 \times 10^{10}\ M_{\odot}$, star-forming galaxies exhibit a size evolution of $R_{e,J} \propto (1+z)^β$ with $β= -0.92 \pm 0.04$, falling between previously reported shallower and steeper measurements. Quiescent galaxies evolve more rapidly, with $β= -1.34 \pm 0.05$, consistent with earlier studies. Among star-forming galaxies, lower-mass systems ($10^{10}$ to $10^{10.5}\ M_{\odot}$) show slower ($β=-0.66\pm0.02$) size evolution compared to their higher-mass counterparts. Furthermore, the surface brightness brightens toward higher redshifts, scaling as $μ_J \propto -2.5 \log(1+z)^γ$. We find $γ= 3.07 \pm 0.08$ for star-forming galaxies and $γ= 3.70 \pm 0.08$ for quiescent galaxies. We also find that massive star-forming galaxies ($M_\star > 10^{10.5}\ M_{\odot}$) exhibit similar $μ_J$ values at fixed redshift, independent of mass. Finally, we demonstrate that the observed surface brightness evolution is driven by the combined evolution of galaxy luminosity and size. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2605_31415 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | COSMOS-Web: Galaxy Size and Surface Brightness Evolution at Rest-Frame 1.22 $μ$m Since $z=3$ Yu, Si-Yue Faisst, Andreas L. Fang, Taotao Toni, Greta Moscardini, Lauro Franco, Maximilien Samir, Rasha M. Hirschmann, Michaela Zhang, Xiaoxia Leroy, Gavin Astrophysics of Galaxies We present the evolution of galaxy size and surface brightness in the rest-frame $J$ band (1.22 $μ$m), tracing the stellar mass distribution, over $0.5 \leq z \leq 3$, using a sample of 15,420 galaxies with stellar masses $M_\star=10^{10}$-$10^{11.5}\ M_{\odot}$ from the JWST COSMOS-Web survey. The rest-frame $J$-band effective radius ($R_{e,J}$) is obtained from previous measurements and mapped from the available JWST/NIRCam filters, while the surface brightness ($μ_J$) is corrected for dust extinction and cosmological dimming. At a characteristic mass of $M_\star = 5 \times 10^{10}\ M_{\odot}$, star-forming galaxies exhibit a size evolution of $R_{e,J} \propto (1+z)^β$ with $β= -0.92 \pm 0.04$, falling between previously reported shallower and steeper measurements. Quiescent galaxies evolve more rapidly, with $β= -1.34 \pm 0.05$, consistent with earlier studies. Among star-forming galaxies, lower-mass systems ($10^{10}$ to $10^{10.5}\ M_{\odot}$) show slower ($β=-0.66\pm0.02$) size evolution compared to their higher-mass counterparts. Furthermore, the surface brightness brightens toward higher redshifts, scaling as $μ_J \propto -2.5 \log(1+z)^γ$. We find $γ= 3.07 \pm 0.08$ for star-forming galaxies and $γ= 3.70 \pm 0.08$ for quiescent galaxies. We also find that massive star-forming galaxies ($M_\star > 10^{10.5}\ M_{\odot}$) exhibit similar $μ_J$ values at fixed redshift, independent of mass. Finally, we demonstrate that the observed surface brightness evolution is driven by the combined evolution of galaxy luminosity and size. |
| title | COSMOS-Web: Galaxy Size and Surface Brightness Evolution at Rest-Frame 1.22 $μ$m Since $z=3$ |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2605.31415 |