An almost NIRCam-dark dusty star-forming galaxy at z=6.63

Abstract We present AC-2168, an almost NIRCam-dark, millimetre-bright galaxy. The source was identified blindly in ALMA Band-4 continuum data and remains undetected in the COSMOS-Web DR1 NIRCam catalogue. We spectroscopically confirm a redshift of zspec = 6.631 from [C ii] 158 μm and four tentatively detected CO lines in NOEMA and ALMA data. SED fitting to near-IR to millimetre photometry yields $L_{\rm IR}=1.6^{+0.6}_{-0.4}\times 10^{12}\, L_\odot$, ${\rm SFR}=244^{+82}_{-55}\, M_\odot \, \rm yr^{-1}$, $M_\star =3.7^{+12.2}_{-2.6}\times 10^{10}\, M_\odot$ and AV = 5.4 ± 1.6 mag. From the millimetre continuum and [C ii] emission, we infer a warm ISM with Tdust = 60 ± 11K, $M_{\rm dust}=3.0^{+0.8}_{-0.5}\times 10^{8}\, M_\odot$ and Mgas = 4.1 ± 0.8 × 1010 M⊙. AC-2168 differs from normal UV-selected galaxies in its strong dust obscuration, yet its moderate SFR at high M⋆, consistent with the star-forming main sequence, distinguishes it from most blindly detected DSFGs dominated by intense starbursts. Its short depletion time of $\sim 170\, \rm Myr$, compact ($\sim 1\, \rm kpc$) dust-continuum size, and moderate SFR suggest a massive system caught in a rapid transition near the end of its main assembly phase, consistent with NIRSpec-based SFHs of massive quiescent galaxies at z ∼ 4 − 5. We also estimate a space density of $\rm 7.8^{+18.0}_{-6.5}\times 10^{-6}\, cMpc^{-3}$ for AC-2168-like NIRCam-dark galaxies at z ∼ 6 − 7, which reaches ∼42% of the abundance of massive quiescent galaxies at z ∼ 4 − 5. These results jointly suggest that NIRCam-dark galaxies are likely the direct progenitors of a substantial fraction of massive quiescent galaxies.

Authors

Institutions

Publication Details

Journal
Monthly Notices of the Royal Astronomical Society
Published
2026-05-13
DOI
https://doi.org/10.1093/mnras/stag846
Primary Topic
Galaxies: Formation, Evolution, Phenomena
Type
article
Field-Weighted Citation Impact
0.00
Controls
|||
ALL TIME
JAN
FEB
MAR
APR
MAY
JUN
JUL
AUG
SEP
OCT
article

An almost NIRCam-dark dusty star-forming galaxy at z=6.63

Louise Paquereau, Stephen M. Wilkins, D. B. Sanders, Santosh Harish et al.
Monthly Notices of the Royal Astronomical Society
Galaxies: Formation, Evolution, Phenomena
article

An almost NIRCam-dark dusty star-forming galaxy at z=6.63

Louise Paquereau, Stephen M. Wilkins, D. B. Sanders, Santosh Harish, Marko Shuntov, Hollis B. Akins, N. Ponthieu, Shuowen Jin, C. M. Casey, G. Lagache, H. J. McCracken, Seb Oliver, Sylvia Adscheid, M. Dessauges‐Zavadsky, Olivia R. Cooper, L. Bing, Maximilien Franco, A. Beelen, Pascal A. Oesch, Jason Rhodes, Brant E. Robertson, Arianna S. Long, B. Magnelli, Steven Gillman, Mengyuan Xiao, Daizhong Liu, Andreas L. Faisst, Jeyhan S. Kartaltepe, Anton M. Koekemoer, R. Neri
article en

Abstract

Abstract We present AC-2168, an almost NIRCam-dark, millimetre-bright galaxy. The source was identified blindly in ALMA Band-4 continuum data and remains undetected in the COSMOS-Web DR1 NIRCam catalogue. We spectroscopically confirm a redshift of zspec = 6.631 from [C ii] 158 μm and four tentatively detected CO lines in NOEMA and ALMA data. SED fitting to near-IR to millimetre photometry yields $L_{\rm IR}=1.6^{+0.6}_{-0.4}\times 10^{12}\, L_\odot$, ${\rm SFR}=244^{+82}_{-55}\, M_\odot \, \rm yr^{-1}$, $M_\star =3.7^{+12.2}_{-2.6}\times 10^{10}\, M_\odot$ and AV = 5.4 ± 1.6 mag. From the millimetre continuum and [C ii] emission, we infer a warm ISM with Tdust = 60 ± 11K, $M_{\rm dust}=3.0^{+0.8}_{-0.5}\times 10^{8}\, M_\odot$ and Mgas = 4.1 ± 0.8 × 1010 M⊙. AC-2168 differs from normal UV-selected galaxies in its strong dust obscuration, yet its moderate SFR at high M⋆, consistent with the star-forming main sequence, distinguishes it from most blindly detected DSFGs dominated by intense starbursts. Its short depletion time of $\sim 170\, \rm Myr$, compact ($\sim 1\, \rm kpc$) dust-continuum size, and moderate SFR suggest a massive system caught in a rapid transition near the end of its main assembly phase, consistent with NIRSpec-based SFHs of massive quiescent galaxies at z ∼ 4 − 5. We also estimate a space density of $\rm 7.8^{+18.0}_{-6.5}\times 10^{-6}\, cMpc^{-3}$ for AC-2168-like NIRCam-dark galaxies at z ∼ 6 − 7, which reaches ∼42% of the abundance of massive quiescent galaxies at z ∼ 4 − 5. These results jointly suggest that NIRCam-dark galaxies are likely the direct progenitors of a substantial fraction of massive quiescent galaxies.

Monthly Notices of the Royal Astronomical Society
California Institute of Technology (US), University of Copenhagen (DK), Centre National de la Recherche Scientifique (FR), Space Telescope Science Institute (US), Planetary Science Institute (US), University of Hawaii System (US), Jet Propulsion Laboratory (US), University of Bonn (DE), Joint Institute for Laboratory Astrophysics (US), University of California, Santa Barbara (US), Rochester Institute of Technology (US), University of Sussex (GB), University of California, Santa Cruz (US), University of Washington (US), Commissariat à l'Énergie Atomique et aux Énergies Alternatives (FR), Université Paris-Saclay (FR), Institut d'Astrophysique de Paris (FR), Purple Mountain Observatory (CN), Sorbonne Université (FR), Astrophysique, Instrumentation et Modélisation (FR), Institut de Radioastronomie Millimétrique (FR), Laboratoire d’Astrophysique de Marseille (FR), DAWN Center for Independent Living (US), CEA Paris-Saclay (FR), Seattle University (US), Geneva College (US), The University of Texas at Austin (US), Université Grenoble Alpes (FR), Technical University of Denmark (DK)
Openalex Percentile: Top 99%
Galaxies: Formation, Evolution, Phenomena
DOIOpen Access PDFOpenAlex
AI Navigator

Ask Laika to Summarize, Analyze, and Connect papers live on the map.

Summarize Papers & Methodologies

Extract key findings, datasets, and comparative methods across publications.

Benchmark Rankings & Visual Analytics

Rank top research institutions, authors, funders, topics, and journals by Field-Weighted Citation Impact (FWCI) and paper volume with instant charts.

Connect Distant Disciplines

Bridge topological clusters on the map to find hidden collaborative intersections.