RIOJA. A Clumpy Galaxy Assembly at Redshift 6.81 Revealed by JWST
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| Main Authors: | , , , , , , , , , , , , , , , , , , , , , , , |
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| Format: | Preprint |
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2025
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| author | Mawatari, Ken Costantin, Luca Usui, Mitsutaka Hashimoto, Takuya Álvarez-Márquez, Javier Sugahara, Yuma Colina, Luis Inoue, Akio K. Osone, Wataru Arribas, Santiago Marques-Chaves, Rui Nakazato, Yurina Hagimoto, Masato Hashigaya, Takeshi Ceverino, Daniel Yoshida, Naoki Bakx, Tom J. L. C. Fudamoto, Yoshinobu Gómez, Alejandro Crespo Matsuo, Hiroshi Pereira-Santaella, Miguel Blanco-Prieto, Carmen Ren, Yi W. Tamura, Yoichi |
| author_facet | Mawatari, Ken Costantin, Luca Usui, Mitsutaka Hashimoto, Takuya Álvarez-Márquez, Javier Sugahara, Yuma Colina, Luis Inoue, Akio K. Osone, Wataru Arribas, Santiago Marques-Chaves, Rui Nakazato, Yurina Hagimoto, Masato Hashigaya, Takeshi Ceverino, Daniel Yoshida, Naoki Bakx, Tom J. L. C. Fudamoto, Yoshinobu Gómez, Alejandro Crespo Matsuo, Hiroshi Pereira-Santaella, Miguel Blanco-Prieto, Carmen Ren, Yi W. Tamura, Yoichi |
| contents | Spatially resolved multi-wavelength analysis is essential to study galaxy formation and evolution. A UV-bright galaxy COS-2987030247 at $z = 6.81$ is one of the Rosetta Stones in the epoch of reionization for which JWST NIRSpec Integral Field Spectroscopy, NIRCam imaging, and ALMA data are available thanks to the RIOJA program. We identified the rest-frame optical emission lines from the ionized hydrogen, oxygen, and neon gas. The \OIII\,5008Å line emission and the NIRCam images show a complex kinematical and morphological structure where two bright main and three faint clumps are identified in a 10 kpc extent. The system is not classified as a purely rotation-dominated disk. The multiple clumps are instead consistent with a merger-related origin, including either distinct galaxies in interaction or star-forming clumps formed through tidal gas compression during a merger. The spatially resolved emission line fluxes show that dust attenuation, metal enrichment, and ionization parameter are preferentially enhanced in the star formation peaks. Our SED fitting suggests that the main clumps are in a moderately dust-attenuated star forming phase ($A_{\rm V} = 0.2$--$0.3$ and SFR(H$α$) $\sim 10$\,M$_\odot$\,yr$^{-1}$) with almost zero escape fraction of ionizing photons. In contrast, the sub-clumps are dust-free and lying on or below the main sequence of star-forming galaxies. These sub-clumps may work as a perturber that triggers the clumpy starburst in the surrounding gas through the merger event. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2507_02053 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | RIOJA. A Clumpy Galaxy Assembly at Redshift 6.81 Revealed by JWST Mawatari, Ken Costantin, Luca Usui, Mitsutaka Hashimoto, Takuya Álvarez-Márquez, Javier Sugahara, Yuma Colina, Luis Inoue, Akio K. Osone, Wataru Arribas, Santiago Marques-Chaves, Rui Nakazato, Yurina Hagimoto, Masato Hashigaya, Takeshi Ceverino, Daniel Yoshida, Naoki Bakx, Tom J. L. C. Fudamoto, Yoshinobu Gómez, Alejandro Crespo Matsuo, Hiroshi Pereira-Santaella, Miguel Blanco-Prieto, Carmen Ren, Yi W. Tamura, Yoichi Astrophysics of Galaxies Spatially resolved multi-wavelength analysis is essential to study galaxy formation and evolution. A UV-bright galaxy COS-2987030247 at $z = 6.81$ is one of the Rosetta Stones in the epoch of reionization for which JWST NIRSpec Integral Field Spectroscopy, NIRCam imaging, and ALMA data are available thanks to the RIOJA program. We identified the rest-frame optical emission lines from the ionized hydrogen, oxygen, and neon gas. The \OIII\,5008Å line emission and the NIRCam images show a complex kinematical and morphological structure where two bright main and three faint clumps are identified in a 10 kpc extent. The system is not classified as a purely rotation-dominated disk. The multiple clumps are instead consistent with a merger-related origin, including either distinct galaxies in interaction or star-forming clumps formed through tidal gas compression during a merger. The spatially resolved emission line fluxes show that dust attenuation, metal enrichment, and ionization parameter are preferentially enhanced in the star formation peaks. Our SED fitting suggests that the main clumps are in a moderately dust-attenuated star forming phase ($A_{\rm V} = 0.2$--$0.3$ and SFR(H$α$) $\sim 10$\,M$_\odot$\,yr$^{-1}$) with almost zero escape fraction of ionizing photons. In contrast, the sub-clumps are dust-free and lying on or below the main sequence of star-forming galaxies. These sub-clumps may work as a perturber that triggers the clumpy starburst in the surrounding gas through the merger event. |
| title | RIOJA. A Clumpy Galaxy Assembly at Redshift 6.81 Revealed by JWST |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2507.02053 |