A dense, metal-rich absorber driven by a heavily dust-obscured galaxy: The direct evidence of CGM enrichment at $z\sim7$
Year: 2026
Type: preprint
Abstract: We report the serendipitous discovery of a dense, metal-enriched circumgalactic medium (CGM) absorber at z=7.03, together with its host galaxy, identified along the sightline toward a red quasar. The absorber exhibits the largest rest-frame equivalent widths and column densities observed to date at z>5, tracing a metal-enriched gaseous halo. Using deep JWST/NIRSpec and NOEMA observations, we characterize the absorber's physical properties and identify its host, ND1, as a vigorously star-forming galaxy at an exceptionally close impact parameter of ~16kpc, so heavily dust-obscured that it is detected only in the longest-wavelength NIRCam bands. Detections of [OIII]$λ$5007, H$α$, and [CII]$λ158\,μ$m emission anchor the systemic redshift to z~7.0321, revealing a coherent ~50km/s blueshift of the absorbing gas relative to the host, suggesting outflow-driven metal transport into the halo. The outflow velocity, combined with the measured column density, implies an outflow rate of $\dot{M}_{\rm out}=64 M_\odot\,yr^{-1}$ and a mass loading factor $η=3$, indicating an energetic, chemically-enriched wind launched from a dust-obscured starburst. While the overall ionization state and [Mg/Fe] ratio align with empirical cosmic evolutionary trends, the absorber displays an enhanced carbon-to-oxygen ([C/O]) ratio. This abundance pattern suggests the nucleosynthetic yields of Population~III stellar explosions, and aligns with the host's star-formation history extending to $z \gtrsim 8$, potentially offering a rare fossil record of primordial metal enrichment. Our findings demonstrate that intense star-formation feedback can rapidly and efficiently pollute the CGM/IGM well into the Epoch of Reionization. The NIR-dark nature of the host further implies that rest-UV surveys may systematically miss the dusty sources that drive CGM- and IGM-scale metal enrichment in the early Universe.
Source: arXiv (Cornell University)
Authors: Fei, Qinyue, Fujimoto, Seiji, Brammer, Gabriel, Christensen, Lise, Vestergaard, Marianne, Naidu, Rohan P., Simcoe, Robert A., Murray, Norman, Ho, Luis C., Li, Ruancun, Bromm, Volker, Álvarez-Márquez, Javier, Akins, Hollis B., Asada, Yoshihisa, Di Stefano, Simona, Inayoshi, Kohei, Kokorev, Vasily, Matthee, Jorryt, Meyer, Romain A., Polzin, Ava, Valentino, Francesco, Walter, Fabian, Neeleman, Marcel, Wu, Yunjing, Xiao, Mengyuan
Institutions: University of Toronto, University of Copenhagen, University of Arizona, Massachusetts Institute of Technology, Canadian Institute for Theoretical Astrophysics, Peking University, Max Planck Institute for Extraterrestrial Physics, Centro de Astrobiología, The University of Texas at Austin, Institute of Science and Technology Austria, University of Geneva, University of Chicago, DTU Space, Technical University of Denmark, National Radio Astronomy Observatory, Kavli Institute for the Physics and Mathematics of the Universe, The University of Tokyo Institutes for Advanced Study, The University of Tokyo
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7213520998