Redshifted Cool Gas in the Disturbed HI 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. HST/COS spectra show low-ionization absorbers redshifted relative to the systemic velocity, most clearly in SII (Δv=19.8±2.6 km s−1) and supported by MgII (Δv=30.3±3.0 km s−1), while PII remains tentative (Δv=7.5±3.4 km s−1). The Keck/HIRES spectra also reveal a redshifted CaII absorption component (Δv=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 is moving away from the observer and toward the background UV source in projection. A VLA--THINGS HI spectrum extracted at the COS position within one VLA beam also shows a redshifted neutral component at vhel=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 HI component. The FAST HI 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 HI component, and the disturbed large-scale HI 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 non-circular disk motions cannot be fully excluded.
Versions
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BibTeX
@misc{yan2026redshifted,
title = {{Redshifted Cool Gas in the Disturbed HI Disk of the Starburst Dwarf NGC 4214}},
author = {Shulan Yan and Taotao Fang and Xiaochuan Jiang and Junfeng Wang and Qingzheng Yu and Chuanpeng Zhang and Ming Zhu},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.13039},
eprint = {2610.13039},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.13039},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Redshifted Cool Gas in the Disturbed HI Disk of the Starburst Dwarf NGC 4214
AU - Shulan Yan
AU - Taotao Fang
AU - Xiaochuan Jiang
AU - Junfeng Wang
AU - Qingzheng Yu
AU - Chuanpeng Zhang
AU - Ming Zhu
PY - 2026
DA - 2026/10/09
PB - arXiv
DO - 10.48550/arxiv.2610.13039
UR - https://arxiv.org/abs/2610.13039
AB - We report redshifted cool gas toward the central star-forming region of the nearby starburst dwarf galaxy NGC 4214. HST/COS spectra show low-ionization absorbers redshifted relative to the systemic velocity, most clearly in SII (Δv=19.8±2.6 km s^−1) and supported by MgII (Δv=30.3±3.0 km s^−1), while PII remains tentative (Δv=7.5±3.4 km s^−1). The Keck/HIRES spectra also reveal a redshifted CaII absorption component (Δv=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 is moving away from the observer and toward the background UV source in projection. A VLA--THINGS HI 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 HI component. The FAST HI 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 HI component, and the disturbed large-scale HI 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 non-circular disk motions cannot be fully excluded.
ER -