Multiwavelength probes of the Milky Way’s cold interstellar medium: radio H <scp>i</scp> and optical K <scp>i</scp> absorption with GASKAP and GALAH

ABSTRACT We present a comparative analysis of interstellar hydrogen (H i) and potassium (K i) absorption from the radio and optical surveys, GASKAP (Galactic Australian Square Kilometre Array Pathfinder) and GALAH (Galactic Archaeology with HERMES), to study the physical and kinematic properties of the cold interstellar medium (ISM) in the Milky Way foreground towards the Magellanic Clouds. By comparing GASKAP H i absorption with interstellar K i absorption detected in GALAH spectra of nearby stars (within 12 arcmin angular distance or a spatial separation of $\sim$0.75 pc), we reveal a strong kinematic correlation between these two tracers of the cold neutral ISM. The velocity offsets between matched H i and K i absorption components are small, with a mean (median) offset of –1.3 (–1.2) $\mathrm{km\, s^{-1}}$ and a standard deviation of 2.3 $\mathrm{km\, s^{-1}}$. The high degree of kinematic consistency suggests a close spatial association between K i and cold H i gas. Correlation analyses reveal a moderate positive relationship between H i and K i line-of-sight properties, such as K i column density with H i column density or H i brightness temperature. We observe a $\sim$63 per cent overlap in the detection of both species towards 290 (out of 462) GASKAP H i absorption lines of sight, and estimate a median K i/H i abundance ratio of $\sim 2.3\times 10^{-10}$, in excellent agreement with previous findings. Our work opens up an exciting avenue of Galactic research that uses large-scale surveys in the radio and optical wavelengths to probe the neutral ISM through its diverse tracers.

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Journal
Monthly Notices of the Royal Astronomical Society
Published
2025-10-03
DOI
https://doi.org/10.1093/mnras/staf1663
Primary Topic
Astrophysics and Star Formation Studies
Type
article
Field-Weighted Citation Impact
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article

Multiwavelength probes of the Milky Way’s cold interstellar medium: radio H i and optical K i absorption with GASKAP and GALAH

Snežana Stanimirović, Yik Ki, N. M. McClure‐Griffiths, E. Müller et al.
Monthly Notices of the Royal Astronomical Society
Astrophysics and Star Formation Studies
article

Multiwavelength probes of the Milky Way’s cold interstellar medium: radio H i and optical K i absorption with GASKAP and GALAH

Snežana Stanimirović, Yik Ki, N. M. McClure‐Griffiths, E. Müller, Sven Buder, Gyueun Park, Nickolas M. Pingel, J. R. Dawson, Jacco Th. van Loon, Hilay Shah, Callum Lynn, John M. Dickey, Claire E. Murray, D. A. Leahy, Antoine Marchal, Helga Dénes, I.J. Kemp, Hiep Nguyen, M.-A. Miville-Deschênes, Min-Young Lee, James Dempsey, J. D. Soler
article en

Abstract

ABSTRACT We present a comparative analysis of interstellar hydrogen (H i) and potassium (K i) absorption from the radio and optical surveys, GASKAP (Galactic Australian Square Kilometre Array Pathfinder) and GALAH (Galactic Archaeology with HERMES), to study the physical and kinematic properties of the cold interstellar medium (ISM) in the Milky Way foreground towards the Magellanic Clouds. By comparing GASKAP H i absorption with interstellar K i absorption detected in GALAH spectra of nearby stars (within 12 arcmin angular distance or a spatial separation of $\sim$0.75 pc), we reveal a strong kinematic correlation between these two tracers of the cold neutral ISM. The velocity offsets between matched H i and K i absorption components are small, with a mean (median) offset of –1.3 (–1.2) $\mathrm{km\, s^{-1}}$ and a standard deviation of 2.3 $\mathrm{km\, s^{-1}}$. The high degree of kinematic consistency suggests a close spatial association between K i and cold H i gas. Correlation analyses reveal a moderate positive relationship between H i and K i line-of-sight properties, such as K i column density with H i column density or H i brightness temperature. We observe a $\sim$63 per cent overlap in the detection of both species towards 290 (out of 462) GASKAP H i absorption lines of sight, and estimate a median K i/H i abundance ratio of $\sim 2.3\times 10^{-10}$, in excellent agreement with previous findings. Our work opens up an exciting avenue of Galactic research that uses large-scale surveys in the radio and optical wavelengths to probe the neutral ISM through its diverse tracers.

Monthly Notices of the Royal Astronomical SocietyVol. 543(4)
Australian National University (AU), Commonwealth Scientific and Industrial Research Organisation (AU), Centre National de la Recherche Scientifique (FR), Space Telescope Science Institute (US), University of Tasmania (AU), Australia Telescope National Facility (AU), University of Wisconsin System (US), University of Wisconsin–Madison (US), Johns Hopkins University (US), University of Calgary (CA), Délégation Paris 7 (FR), Université Paris Cité (FR), Curtin University (AU), Commissariat à l'Énergie Atomique et aux Énergies Alternatives (FR), Université Paris-Saclay (FR), Korea Astronomy and Space Science Institute (KR), Universidad Yachay Tech (EC), Astrophysique, Instrumentation et Modélisation (FR), ASTRO-3D (AU), Institute for Space Astrophysics and Planetology (IT), Université Bourgogne Franche-Comté (FR), CEA Paris-Saclay (FR), ARC Centre of Excellence for All-sky Astrophysics (AU), Max Planck Institute for Radio Astronomy (DE), International Centre for Radio Astronomy Research (AU), Keele University (GB), University of Baltimore (US), Netherlands Institute for Radio Astronomy (NL), Macquarie University (AU)
National Science Foundation, University of Wisconsin-Madison, Science and Industry Endowment Fund, Australian Government, European Space Agency, Commonwealth Scientific and Industrial Research Organisation, Government of Western Australia, Australian Astronomical Optics-Macquarie, Division of Graduate Education
Openalex Percentile: Top 81%
Astrophysics and Star Formation Studies
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