Disturbed Cold Gas in Galaxy and Structure Formation

Abstract The cold gas in the circumgalactic medium (CGM) and its interaction with galaxies remain poorly understood. Strong Mg ii ( λλ 2796, 2803) absorptions seen in background quasar spectra reveal large reservoirs of neutral hydrogen, potentially serving as progenitors of star-forming galaxies at high redshifts. In this study, we search for galaxies in the vicinity of very strong Mg ii absorbers (rest-frame equivalent width W r > 2 Å) with high kinematic velocities (>500 km s −1 ) at 2.0 < z < 6.0. Observations were conducted with the Very Large Telescope/MUSE, JWST/NIRCam, and the Atacama Large Millimeter/submillimeter Array to detect Ly α and nebular emission lines and dust continuum emission. We identify two Ly α emitters associated with a strong Mg ii absorber pair, separated by ∼1000 km s −1 at z ∼ 4.87, in the vicinity of quasar J1306+0356. We observe relative differences in metallicity, dust content, and ionization states in this ultralarge absorption pair system, indicating potential metal and dust transfer within the system. For another strong Mg ii absorber at z = 2.5662 ( W r = 2.638 ± 0.124 Å), toward a second quasar J0305–3150, we detect a dusty star-forming galaxy at a projected distance of D = 38 kpc. This galaxy exhibits prominent He i , [S iii ], and Paschen γ lines, along with significant dust continuum. It has a star formation rate of ∼121 ± 33 M ⊙ yr −1 and likely harbors a rotating disk. These findings tentatively suggest that cold gas at high redshifts fuels disk formation and participates in metal and dust transfer within overdense CGM regions.

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Publication Details

Journal
The Astrophysical Journal Letters
Published
2025-11-27
DOI
https://doi.org/10.3847/2041-8213/ae1234
Primary Topic
Astrophysics and Star Formation Studies
Type
article
Field-Weighted Citation Impact
0.00

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article

Disturbed Cold Gas in Galaxy and Structure Formation

Xiaohui Fan, Jinyi Yang, Jaclyn B. Champagne, Weizhe Liu et al.
The Astrophysical Journal Letters
Astrophysics and Star Formation Studies
article

Disturbed Cold Gas in Galaxy and Structure Formation

Xiaohui Fan, Jinyi Yang, Jaclyn B. Champagne, Weizhe Liu, Fangzhou Jiang, Xiangyu Jin, Siwei Zou, Feige Wang, Luis C. Ho, Jianwei Lyu, Lile Wang, Cheng Cheng, Emanuele Paolo Farina, Céline Péroux, Robert A. Simcoe, Wen Sun, Zihao Li, Jianan Li, Jinning Liang, Xiaojing Lin, P. Petitjean
article en

Abstract

Abstract The cold gas in the circumgalactic medium (CGM) and its interaction with galaxies remain poorly understood. Strong Mg ii ( λλ 2796, 2803) absorptions seen in background quasar spectra reveal large reservoirs of neutral hydrogen, potentially serving as progenitors of star-forming galaxies at high redshifts. In this study, we search for galaxies in the vicinity of very strong Mg ii absorbers (rest-frame equivalent width W r > 2 Å) with high kinematic velocities (>500 km s −1 ) at 2.0 < z < 6.0. Observations were conducted with the Very Large Telescope/MUSE, JWST/NIRCam, and the Atacama Large Millimeter/submillimeter Array to detect Ly α and nebular emission lines and dust continuum emission. We identify two Ly α emitters associated with a strong Mg ii absorber pair, separated by ∼1000 km s −1 at z ∼ 4.87, in the vicinity of quasar J1306+0356. We observe relative differences in metallicity, dust content, and ionization states in this ultralarge absorption pair system, indicating potential metal and dust transfer within the system. For another strong Mg ii absorber at z = 2.5662 ( W r = 2.638 ± 0.124 Å), toward a second quasar J0305–3150, we detect a dusty star-forming galaxy at a projected distance of D = 38 kpc. This galaxy exhibits prominent He i , [S iii ], and Paschen γ lines, along with significant dust continuum. It has a star formation rate of ∼121 ± 33 M ⊙ yr −1 and likely harbors a rotating disk. These findings tentatively suggest that cold gas at high redshifts fuels disk formation and participates in metal and dust transfer within overdense CGM regions.

The Astrophysical Journal LettersVol. 994(2)
Universidad de Santiago de Chile (CL), University of Copenhagen (DK), Centre National de la Recherche Scientifique (FR), European Southern Observatory (DE), University of Arizona (US), Chinese Academy of Sciences (CN), Peking University (CN), University of Michigan (US), Institut d'Astrophysique de Paris (FR), Kavli Institute for Particle Astrophysics and Cosmology (US), Laboratoire d’Astrophysique de Marseille (FR), Gemini North Observatory (US), Kavli Institute for Theoretical Sciences (CN), National Astronomical Observatories (CN), University of Chile (CL), Tsinghua University (CN)
National Science Foundation, National Aeronautics and Space Administration, Space Telescope Science Institute, National Radio Astronomy Observatory, Agence Nationale de la Recherche, National Natural Science Foundation of China, Chinese Academy of Sciences, Korea Astronomy and Space Science Institute, National Astronomical Observatory of Japan, National Science and Technology Council, National Institutes of Natural Sciences
Openalex Percentile: Top 75%
Astrophysics and Star Formation Studies
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