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Physical origins of outflowing cold clouds in local star-forming dwarf galaxies

We study the physical origins of outflowing cold clouds in a sample of 14 low-redshift dwarf (M* ≲ 1010M⊙) galaxies from the Cosmic Origins Spectrograph Legacy Archive Spectroscopic SurveY (CLASSY) using Keck/ESI data. Outflows are traced by broad (FWHM ∼260 km s−1) and very-broad (VB; FWHM ∼1200 km...

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Main Authors: Peng, Zixuan (Author) , Martin, Crystal L. (Author) , Chen, Zirui (Author) , Fielding, Drummond B. (Author) , Xu, Xinfeng (Author) , Heckman, Timothy (Author) , Ramambason, Lise (Author) , Li, Yuan (Author) , Carr, Cody (Author) , Hu, Weida (Author) , Chen, Zuyi (Author) , Scarlata, Claudia (Author) , Henry, Alaina (Author)
Format: Article (Journal)
Language:English
Published: 2025 March 10
In: The astrophysical journal
Year: 2025, Volume: 981, Issue: 2, Pages: 1-35
ISSN:1538-4357
DOI:10.3847/1538-4357/ada606
Online Access:Verlag, kostenfrei, Volltext: https://doi.org/10.3847/1538-4357/ada606
Verlag, kostenfrei, Volltext: https://dx.doi.org/10.3847/1538-4357/ada606
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Author Notes:Zixuan Peng, Crystal L. Martin, Zirui Chen, Drummond B. Fielding, Xinfeng Xu, Timothy Heckman, Lise Ramambason, Yuan Li, Cody Carr, Weida Hu, Zuyi Chen, Claudia Scarlata, and Alaina Henry
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Summary:We study the physical origins of outflowing cold clouds in a sample of 14 low-redshift dwarf (M* ≲ 1010M⊙) galaxies from the Cosmic Origins Spectrograph Legacy Archive Spectroscopic SurveY (CLASSY) using Keck/ESI data. Outflows are traced by broad (FWHM ∼260 km s−1) and very-broad (VB; FWHM ∼1200 km s−1) velocity components in strong emission lines like [O iii] λ5007 and Hα. The maximum velocities () of broad components correlate positively with star formation rate, unlike the anticorrelation observed for VB components, and are consistent with superbubble models. In contrast, supernova-driven galactic wind models better reproduce the of VB components. Direct radiative cooling from a hot wind significantly underestimates the luminosities of both broad and VB components. A multiphase wind model with turbulent radiative mixing reduces this discrepancy to at least 1 dex for most VB components. Stellar photoionization likely provides additional energy since broad components lie in the starburst locus of excitation diagnostic diagrams. We propose a novel interpretation of outflow origins in star-forming dwarf galaxies—broad components trace expanding superbubble shells, while VB components originate from galactic winds. One-zone photoionization models fail to explain the low-ionization lines ([S ii] and [O i]) of broad components near the maximal starburst regime, which two-zone photoionization models with density-bounded channels instead reproduce. These two-zone models indicate anisotropic leakage of Lyman continuum photons through low-density channels formed by expanding superbubbles. Our study highlights extreme outflows () in nine out of 14 star-forming dwarf galaxies, comparable to active galactic nucleus-driven winds.
Item Description:Online verfügbar: 06. März 2025
Gesehen am 09.09.2025
Physical Description:Online Resource
ISSN:1538-4357
DOI:10.3847/1538-4357/ada606

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