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An ATCA survey of HI absorption in the Magellanic Clouds. I. H I gas temperature measurements in the small Magellanic Cloud

Citation

Jameson, K and McClure-Griffiths, NM and Liu, B and Dickey, JM and Staveley-Smith, L and Stanimirovic, S and Dempsey, JM and Dawson, JR and Denes, H and Bolatto, AD and Li, D and Wong, T, An ATCA survey of HI absorption in the Magellanic Clouds. I. H I gas temperature measurements in the small Magellanic Cloud, Astrophysical Journal Supplement Series, 244, (1) pp. 1-17. ISSN 0067-0049 (2019) [Refereed Article]


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2019. The American Astronomical Society. All rights reserved. Licensed under Creative Commons Attribution 4.0 International (CC BY 4.0) https://creativecommons.org/licenses/by/4.0/

DOI: doi:10.3847/1538-4365/ab3576

Abstract

We present the first results from the Small Magellanic Cloud portion of a new Australia Telescope Compact Array H i absorption survey of both of the Magellanic Clouds, comprising over 800 hr of observations. Our new H i absorption line data allow us to measure the temperature and fraction of cold neutral gas in a low-metallicity environment. We observed 22 separate fields, targeting a total of 55 continuum sources, against 37 of which we detected H i absorption; from this we measure a column-density-weighted mean average spin temperature of $\langle {T}_{{\rm{s}}}\rangle $ = 150 K. Splitting the spectra into individual absorption line features, we estimate the temperatures of different gas components and find an average cold gas temperature of ~30 K for this sample, lower than the average of ~40 K in the Milky Way. The H i appears to be evenly distributed throughout the SMC, and we detect absorption in 67% of the lines of sight in our sample, including some outside the main body of the galaxy (NH i $\gt 2\times {10}^{21}$ cm−2). The optical depth and temperature of the cold neutral atomic gas show no strong trend with location spatially or in velocity. Despite the low-metallicity environment, we find an average cold gas fraction of ~20%, not dissimilar from that of the Milky Way.

Item Details

Item Type:Refereed Article
Keywords:galaxies; ISM clouds; Magellanic Clouds; radio lines; ISM
Research Division:Physical Sciences
Research Group:Astronomical sciences
Research Field:Galactic astronomy
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the physical sciences
UTAS Author:Dickey, JM (Professor John Dickey)
UTAS Author:Dawson, JR (Dr Joanne Dawson)
ID Code:152817
Year Published:2019
Web of Science® Times Cited:11
Deposited By:Physics
Deposited On:2022-08-24
Last Modified:2022-09-14
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