NOEMA probes the [CII] and dust content in a 2175Å UV Bump Galaxy at z=7.1
Abstract
The detection of the $2175$Å UV bump at z>6 challenges existing models of dust formation, suggesting rapid formation of small carbonaceous dust grains within the first billion years of cosmic time. We present the results of the first direct attempt at linking far-infrared (FIR) observations to the UV bump within the Epoch of Reionisation (EoR), through NOEMA observations of GNWY-7379420231 at z=7.108, a galaxy exhibiting the strongest known UV bump feature at z>4. We detect the [CII] 158μm emission line at 5.1σ at z[CII] = 7.1078 ± 0.0005, in excellent agreement with the redshift derived from the [OIII] λ5007Å line. The {\cii} luminosity implies SFR[CII]=16.2+5.8−5.5M⊙ yr−1, consistent with short timescale SFR tracers such as dust corrected SFRHα=18.0±3.9 M⊙ yr−1 and SFR10 Myr=20.5+3.8−5.0M⊙ yr−1 from SED fitting. The dust continuum is not detected suggesting an obscured SFR of SFRIR < 32 M⊙ yr−1 and a dust mass of Md < 5.3×106 M⊙ (Md/M⋆<2%). Finally, the [CII]-derived dynamical mass of log10(Mdyn/M⊙)=8.95+0.51−0.66 and stellar mass of log 10(M⋆ / M⊙) = 8.39−0.09+0.13 suggest a gas-rich moderately massive galaxy. Taken together these results rule out GNWY-7379420231 being a heavily dust obscured or massive galaxy, but rather a `normal' EoR galaxy with a recent upturn in star-formation. Our results suggest efficient shattering of larger dust grains in the diffuse, turbulent ISM and/or fortunate line of sight alignment are needed to explain the UV bump properties of GNWY-7379420231.
Related
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BibTeX
@misc{ormerod2026noema,
title = {{NOEMA probes the [CII] and dust content in a 2175Å UV Bump Galaxy at $z=7.1$}},
author = {Katherine Ormerod and Renske Smit and Joris Witstok and Anna de Graaff and Michael V. Maseda and Irene Shivaei and Andrew J. Bunker and Gareth C. Jones},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.12203},
eprint = {2609.12203},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.12203},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - NOEMA probes the [CII] and dust content in a 2175Å UV Bump Galaxy at z=7.1
AU - Katherine Ormerod
AU - Renske Smit
AU - Joris Witstok
AU - Anna de Graaff
AU - Michael V. Maseda
AU - Irene Shivaei
AU - Andrew J. Bunker
AU - Gareth C. Jones
PY - 2026
DA - 2026/09/10
PB - arXiv
DO - 10.48550/arxiv.2609.12203
UR - https://arxiv.org/abs/2609.12203
AB - The detection of the $2175$Å UV bump at z>6 challenges existing models of dust formation, suggesting rapid formation of small carbonaceous dust grains within the first billion years of cosmic time. We present the results of the first direct attempt at linking far-infrared (FIR) observations to the UV bump within the Epoch of Reionisation (EoR), through NOEMA observations of GNWY-7379420231 at z=7.108, a galaxy exhibiting the strongest known UV bump feature at z>4. We detect the [CII] 158μm emission line at 5.1σ at z_[CII] = 7.1078 ± 0.0005, in excellent agreement with the redshift derived from the [OIII] λ5007Å line. The {\cii} luminosity implies SFR_[CII]=16.2^+5.8_−5.5M_⊙ yr^−1, consistent with short timescale SFR tracers such as dust corrected SFR_Hα=18.0±3.9 M_⊙ yr^−1 and SFR_10 Myr=20.5^+3.8_−5.0M_⊙ yr^−1 from SED fitting. The dust continuum is not detected suggesting an obscured SFR of SFR_IR < 32 M_⊙ yr^−1 and a dust mass of M_d < 5.3×10^6 M_⊙ (M_d/M_⋆<2%). Finally, the [CII]-derived dynamical mass of log_10(M_dyn/M_⊙)=8.95^+0.51_−0.66 and stellar mass of log _10(M_⋆ / M_⊙) = 8.39_−0.09^+0.13 suggest a gas-rich moderately massive galaxy. Taken together these results rule out GNWY-7379420231 being a heavily dust obscured or massive galaxy, but rather a `normal' EoR galaxy with a recent upturn in star-formation. Our results suggest efficient shattering of larger dust grains in the diffuse, turbulent ISM and/or fortunate line of sight alignment are needed to explain the UV bump properties of GNWY-7379420231.
ER -