The GASKAP-H I Survey Toward the Magellanic Clouds: Cold Atomic Gas Survival and Evolution in the Large Magellanic Cloud

Abstract We use atomic hydrogen (H I ) absorption detections from the GASKAP-H I survey to investigate the properties of cold atomic gas in the Large Magellanic Cloud (LMC). Using the radiative transfer method, we decompose 155 sightlines into 330 cold neutral medium (CNM), 2 thermally unstable neutral medium (UNM), and 310 warm neutral medium (WNM) components. We find that the CNM in the LMC exhibits higher optical depths (median 0.46), lower spin temperatures (median ∼37 K), broader linewidths (median ∼4.9 km s −1 ), and slightly lower CNM fractions (median ∼23%) than in the Milky Way. We examine the connection between the CNM, molecular gas, and star formation, finding that CNM correlates more closely with molecular gas than WNM, while molecular gas shows a tighter relation with star formation. Molecular hydrogen (H 2 ) formation begins near N HI,CNM ∼ 10 20 cm −2 , and nearly all sightlines with N HI,CNM > 10 21 cm −2 contain molecular gas. The CNM fraction increases with visual extinction ( A V ), and the LMC maintains CNM fractions comparable to those in the Milky Way at substantially lower A V , likely due to higher local densities and a longer line-of-sight depth. Sightlines near expanding shells tend to show higher CNM fractions, although this is partly driven by higher total H I column densities. Finally, the CNM kinematics generally follow the H I disk rotation, with about 7% of components showing velocity offsets greater than 25 km s −1 , likely tracing inflows or outflows driven by stellar feedback or large-scale interactions within the Magellanic system.

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Publication Details

Journal
The Astrophysical Journal
Published
2026-11-11
DOI
https://doi.org/10.3847/1538-4357/ae9f43
Primary Topic
Astrophysics and Star Formation Studies
Type
article
Field-Weighted Citation Impact
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article

The GASKAP-H I Survey Toward the Magellanic Clouds: Cold Atomic Gas Survival and Evolution in the Large Magellanic Cloud

Snežana Stanimirović, N. M. McClure‐Griffiths, Nickolas M. Pingel, Jacco Th. van Loon et al.
2 links
The Astrophysical Journal
Astrophysics and Star Formation Studies
article

The GASKAP-H I Survey Toward the Magellanic Clouds: Cold Atomic Gas Survival and Evolution in the Large Magellanic Cloud

Snežana Stanimirović, N. M. McClure‐Griffiths, Nickolas M. Pingel, Jacco Th. van Loon, Ioana A. Stelea, Lister Staveley‐Smith, John M. Dickey, Claire E. Murray, Denis Alan Leahy, Antoine Marchal, Katherine E. Jameson, Daniel R. Rybarczyk, Ian J. Kemp, Hiep Nguyen, Callum Lynn, James Dempsey, Yik Ki Ma, Min-Young Lee, Steven R. Gibson, Helga D{é}nes, Hongxing Chen
article en

Abstract

Abstract We use atomic hydrogen (H I ) absorption detections from the GASKAP-H I survey to investigate the properties of cold atomic gas in the Large Magellanic Cloud (LMC). Using the radiative transfer method, we decompose 155 sightlines into 330 cold neutral medium (CNM), 2 thermally unstable neutral medium (UNM), and 310 warm neutral medium (WNM) components. We find that the CNM in the LMC exhibits higher optical depths (median 0.46), lower spin temperatures (median ∼37 K), broader linewidths (median ∼4.9 km s −1 ), and slightly lower CNM fractions (median ∼23%) than in the Milky Way. We examine the connection between the CNM, molecular gas, and star formation, finding that CNM correlates more closely with molecular gas than WNM, while molecular gas shows a tighter relation with star formation. Molecular hydrogen (H 2 ) formation begins near N HI,CNM ∼ 10 20 cm −2 , and nearly all sightlines with N HI,CNM > 10 21 cm −2 contain molecular gas. The CNM fraction increases with visual extinction ( A V ), and the LMC maintains CNM fractions comparable to those in the Milky Way at substantially lower A V , likely due to higher local densities and a longer line-of-sight depth. Sightlines near expanding shells tend to show higher CNM fractions, although this is partly driven by higher total H I column densities. Finally, the CNM kinematics generally follow the H I disk rotation, with about 7% of components showing velocity offsets greater than 25 km s −1 , likely tracing inflows or outflows driven by stellar feedback or large-scale interactions within the Magellanic system.

The Astrophysical JournalVol. 1012(1)
Australian National University (AU), California Institute of Technology (US), Space Telescope Science Institute (US), University of Tasmania (AU), University of Wisconsin–Madison (US), Johns Hopkins University (US), The University of Western Australia (AU), Curtin University (AU), Université Paris Sciences et Lettres (FR), Korea Astronomy and Space Science Institute (KR), SKA Observatory (GB), Max Planck Institute for Radio Astronomy (DE), Keele University (GB), Indiana University (US), Universidad San Francisco de Quito (EC), Western Kentucky University (US)
National Science Foundation, National Aeronautics and Space Administration, University of Wisconsin-Madison, Science and Industry Endowment Fund, Australian Government, Commonwealth Scientific and Industrial Research Organisation, Government of Western Australia
Astrophysics and Star Formation Studies
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