Redshifted Cool Gas in the Disturbed H i Disk of the Starburst Dwarf NGC 4214

Abstract We report redshifted cool gas toward the central star-forming region of the nearby starburst dwarf galaxy NGC 4214. Hubble Space Telescope/Cosmic Origins Spectrograph (COS) spectra show low-ionization absorbers redshifted relative to the systemic velocity, most clearly in S ii (Δ v = 19.8 ± 2.6 km s −1 ) and supported by Mg ii (Δ v = 30.3 ± 3.0 km s −1 ), while P ii remains tentative (Δ v = 7.5 ± 3.4 km s −1 ). The Keck/HIRES spectra also reveal a redshifted Ca ii absorption component (Δ v = 25.6 ± 1.5 km s −1 ). Because the absorption is detected against the central UV or optical continuum, the gas must lie in the foreground of the star-forming region and be moving away from the observer and toward the background UV source in projection. A Very Large Array (VLA)–THINGS H i spectrum extracted at the COS position within one VLA beam also shows a redshifted neutral component at v hel = 329.2 ± 0.9 km s −1 , offset by 38.2 ± 1.3 km s −1 from systemic and by 27.6 ± 1.0 km s −1 from the dominant local H i component. The FAST H i mapping further reveals an extended, kinematically disturbed neutral disk, with residual structures relative to a warped-disk model. Together, the redshifted UV absorption, the redshifted H i component, and the disturbed large-scale H i velocity field show that the central anomalous cool gas is observed in a galaxy with a disturbed extended neutral disk. This geometry suggests that the redshifted cool gas may trace inflow or recycled fallback toward the central region, although warped-disk or noncircular disk motions cannot be fully excluded.

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Publication Details

Journal
The Astrophysical Journal Letters
Published
2026-11-03
DOI
https://doi.org/10.3847/2041-8213/aeb26b
Primary Topic
Galaxies: Formation, Evolution, Phenomena
Type
article
Field-Weighted Citation Impact
0.00

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article

Redshifted Cool Gas in the Disturbed H i Disk of the Starburst Dwarf NGC 4214

Taotao Fang, Chuanpeng Zhang, Jiang Xiaochuan, Junfeng Wang et al.
The Astrophysical Journal Letters
Galaxies: Formation, Evolution, Phenomena
article

Redshifted Cool Gas in the Disturbed H i Disk of the Starburst Dwarf NGC 4214

Taotao Fang, Chuanpeng Zhang, Jiang Xiaochuan, Junfeng Wang, Shulan Yan, Ming Zhu, Qingzheng Yu
article en

Abstract

Abstract We report redshifted cool gas toward the central star-forming region of the nearby starburst dwarf galaxy NGC 4214. Hubble Space Telescope/Cosmic Origins Spectrograph (COS) spectra show low-ionization absorbers redshifted relative to the systemic velocity, most clearly in S ii (Δ v = 19.8 ± 2.6 km s −1 ) and supported by Mg ii (Δ v = 30.3 ± 3.0 km s −1 ), while P ii remains tentative (Δ v = 7.5 ± 3.4 km s −1 ). The Keck/HIRES spectra also reveal a redshifted Ca ii absorption component (Δ v = 25.6 ± 1.5 km s −1 ). Because the absorption is detected against the central UV or optical continuum, the gas must lie in the foreground of the star-forming region and be moving away from the observer and toward the background UV source in projection. A Very Large Array (VLA)–THINGS H i spectrum extracted at the COS position within one VLA beam also shows a redshifted neutral component at v hel = 329.2 ± 0.9 km s −1 , offset by 38.2 ± 1.3 km s −1 from systemic and by 27.6 ± 1.0 km s −1 from the dominant local H i component. The FAST H i mapping further reveals an extended, kinematically disturbed neutral disk, with residual structures relative to a warped-disk model. Together, the redshifted UV absorption, the redshifted H i component, and the disturbed large-scale H i velocity field show that the central anomalous cool gas is observed in a galaxy with a disturbed extended neutral disk. This geometry suggests that the redshifted cool gas may trace inflow or recycled fallback toward the central region, although warped-disk or noncircular disk motions cannot be fully excluded.

The Astrophysical Journal LettersVol. 1011(2)
Xiamen University (CN), Chinese Academy of Sciences (CN), Arcetri Astrophysical Observatory (IT), Fujian Business University (CN), National Astronomical Observatories (CN), University of Florence (IT), National Institute for Astrophysics (IT)
Space Telescope Science Institute, National Natural Science Foundation of China, Department of Education, Fujian Province, National Astronomical Observatories, Chinese Academy of Sciences
Openalex Percentile: Top 22%
Galaxies: Formation, Evolution, Phenomena
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