| Issue |
A&A
Volume 708, April 2026
|
|
|---|---|---|
| Article Number | A361 | |
| Number of page(s) | 7 | |
| Section | Extragalactic astronomy | |
| DOI | https://doi.org/10.1051/0004-6361/202556655 | |
| Published online | 27 April 2026 | |
A NOEMA pilot survey of [C II] line emission in luminous galaxies at z ≈ 6
1
Departamento de Astronomía, Universidad de Concepción, Barrio Universitario, Concepción, Chile
2
Millenium Nucleus for Galaxies (MINGAL), Concepción, Chile
3
Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany
4
Purple Mountain Observatory, Chinese Academy of Sciences, 10 Yuanhua Road, Nanjing 210023, China
5
Institute for Cosmic Ray Research, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8582, Japan
6
Institut de Radioastronomie Millimétrique (IRAM), 300 Rue de la Piscine, 38400 Saint-Martin-d’Hères, France
★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.
Received:
29
July
2025
Accepted:
21
February
2026
Abstract
We present Northern Extended Millimeter Array (NOEMA) observations of four luminous galaxies at z ∼ 6, when the Universe was less than ∼1 Gyr old. These galaxies are detected in the [C II] 158 μm fine-structure line, and three also exhibit underlying dust continuum emission. The [C II] line velocities are offset by a few hundred kilometers per second relative to the Lyα emission, possibly indicating the presence of outflows or a large reservoir of surrounding atomic gas. From the combination of dust continuum and rest-frame UV emission, we estimate that approximately 50% of the star formation is obscured by dust, consistent with values found in other massive star-forming galaxies at similar redshifts. The [C II]-to-far-infrared (FIR) luminosity ratios of the continuum-detected galaxies are elevated compared to nearby galaxies with similar FIR luminosities. In one system, J163026+4315, the [C II] emission is spatially resolved, allowing us to measure the source size and FIR surface brightness (ΣFIR). We find that the [C II]/FIR as a function of ΣFIR in this source follows the trends observed in both local and high-redshift galaxy populations. A kinematic analysis of the resolved [C II] emission provides tentative evidence for a rotating disk, although higher-angular resolution data are needed to confirm this. These results demonstrate the power of NOEMA to probe the physical conditions and structure of the interstellar medium in galaxies in the first billion years of cosmic history.
Key words: galaxies: high-redshift / galaxies: ISM / galaxies: structure
© The Authors 2026
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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