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| Main Authors: | , , , , , , , , , , , , , , , , , , |
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| Format: | Preprint |
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2025
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| Online Access: | https://arxiv.org/abs/2506.21674 |
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| _version_ | 1866918293093220352 |
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| author | Endsley, Ryan Shapley, Alice E. Topping, Michael W. Stark, Daniel P. Bouwens, Rychard J. Rowland, Lucie E. Sommovigo, Laura Algera, Hiddo S. B. Aravena, Manuel Bowler, Rebecca A. A. da Cunha, Elisabete de Looze, Ilse Ferrara, Andrea Fisher, Rebecca González, Valentino Inami, Hanae Nanayakkara, Themiya Schouws, Sander Tang, Mengtao |
| author_facet | Endsley, Ryan Shapley, Alice E. Topping, Michael W. Stark, Daniel P. Bouwens, Rychard J. Rowland, Lucie E. Sommovigo, Laura Algera, Hiddo S. B. Aravena, Manuel Bowler, Rebecca A. A. da Cunha, Elisabete de Looze, Ilse Ferrara, Andrea Fisher, Rebecca González, Valentino Inami, Hanae Nanayakkara, Themiya Schouws, Sander Tang, Mengtao |
| contents | We present Keck/MOSFIRE H-band spectroscopic measurements covering the [CIII]1907, CIII]1909 doublet for a sample of 8 z~7 spectroscopically-confirmed star-forming galaxies drawn from the Reionization Era Bright Emission Line Survey (REBELS). This REBELS-MOSFIRE sample is notable for its bright median UV luminosity (Muv=-22.5 AB) and large median stellar mass (log(Mstar/Msun)=9.2). Although three sources show tentative evidence of a CIII] detection, we obtain no confident detections for any of the 8 REBELS-MOSFIRE sources. The median [CIII]1907+CIII]1909 3-sigma upper limit in equivalent width (EW) for the REBELS-MOSFIRE sample is 6.5 AA, and a stack of their H-band MOSFIRE spectra yields a non-detection with an associated 3-sigma upper limit of 2.6 AA. These upper limits fall significantly below the CIII] EW measured in a composite spectrum of representative z~7 star-forming galaxies, as well as those measured for notable early star-forming galaxies such as GN-z11, GHZ2, GS-z12, and RXCJ2248-ID. The lack of strong CIII] emission can be understood within the context of the stellar populations of the REBELS galaxies, as well as the ionization conditions and gas-phase metallicity implied by rest-frame optical spectroscopic properties ([OIII]+Hb EWs, and [OIII]5007/[OII]3727 and [NeIII]3869/[OII]3727 line ratios). The REBELS-MOSFIRE sample represents the higher-mass, higher-metallicity, lower-excitation tail of the z~7 galaxy population, whose ionizing properties must be fully characterized to constrain the role of star-forming galaxies during cosmic reionization. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2506_21674 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | REBELS-MOSFIRE: Weak CIII] Emission is Typical Among Extremely UV-bright, Massive Galaxies at $z\sim7$ Endsley, Ryan Shapley, Alice E. Topping, Michael W. Stark, Daniel P. Bouwens, Rychard J. Rowland, Lucie E. Sommovigo, Laura Algera, Hiddo S. B. Aravena, Manuel Bowler, Rebecca A. A. da Cunha, Elisabete de Looze, Ilse Ferrara, Andrea Fisher, Rebecca González, Valentino Inami, Hanae Nanayakkara, Themiya Schouws, Sander Tang, Mengtao Astrophysics of Galaxies We present Keck/MOSFIRE H-band spectroscopic measurements covering the [CIII]1907, CIII]1909 doublet for a sample of 8 z~7 spectroscopically-confirmed star-forming galaxies drawn from the Reionization Era Bright Emission Line Survey (REBELS). This REBELS-MOSFIRE sample is notable for its bright median UV luminosity (Muv=-22.5 AB) and large median stellar mass (log(Mstar/Msun)=9.2). Although three sources show tentative evidence of a CIII] detection, we obtain no confident detections for any of the 8 REBELS-MOSFIRE sources. The median [CIII]1907+CIII]1909 3-sigma upper limit in equivalent width (EW) for the REBELS-MOSFIRE sample is 6.5 AA, and a stack of their H-band MOSFIRE spectra yields a non-detection with an associated 3-sigma upper limit of 2.6 AA. These upper limits fall significantly below the CIII] EW measured in a composite spectrum of representative z~7 star-forming galaxies, as well as those measured for notable early star-forming galaxies such as GN-z11, GHZ2, GS-z12, and RXCJ2248-ID. The lack of strong CIII] emission can be understood within the context of the stellar populations of the REBELS galaxies, as well as the ionization conditions and gas-phase metallicity implied by rest-frame optical spectroscopic properties ([OIII]+Hb EWs, and [OIII]5007/[OII]3727 and [NeIII]3869/[OII]3727 line ratios). The REBELS-MOSFIRE sample represents the higher-mass, higher-metallicity, lower-excitation tail of the z~7 galaxy population, whose ionizing properties must be fully characterized to constrain the role of star-forming galaxies during cosmic reionization. |
| title | REBELS-MOSFIRE: Weak CIII] Emission is Typical Among Extremely UV-bright, Massive Galaxies at $z\sim7$ |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2506.21674 |