Repository logo

The Diffuse Ionized Gas Halo of the Large Magellanic Cloud

Published version

Repository DOI

Change log


jats:titleAbstract</jats:title> jats:pThe Large Magellanic Cloud (LMC) has an extensive Hjats:italicα</jats:italic> emission halo that traces an extended, warm ionized component of its interstellar medium. Using the Wisconsin Hjats:italicα</jats:italic> Mapper telescope, we present the first kinematic Hjats:italicα</jats:italic> survey of an extensive region around the LMC, from (jats:italicℓ</jats:italic>, jats:italicb</jats:italic>) = (264.°5, − 45.°5) to (295.°5, − 19.°5), covering +150 ≤ jats:italicv</jats:italic> jats:subLSR</jats:sub> ≤ + 390 km sjats:sup−1</jats:sup>. We find that ionized hydrogen exists throughout the galaxy and extends several degrees beyond detected neutral hydrogen emission jats:inline-formula jats:tex-math

</jats:tex-math> <mml:math xmlns:mml="" overflow="scroll"> <mml:mo stretchy="false">(</mml:mo> mml:milog</mml:mi> <mml:mfenced close=")" open="("> mml:mrow mml:msub mml:mrow mml:miN</mml:mi> </mml:mrow> mml:mrow <mml:mi mathvariant="normal">H</mml:mi> <mml:mspace width="0.25em" /> <mml:mi mathsize="small" mathvariant="normal">I</mml:mi> mml:mrow <mml:mo stretchy="true">/</mml:mo> </mml:mrow> mml:msup mml:mrow mml:micm</mml:mi> </mml:mrow> mml:mrow mml:mo−</mml:mo> mml:mn2</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:msub> </mml:mrow> </mml:mfenced> mml:mo≈</mml:mo> mml:mn18.3</mml:mn> <mml:mo stretchy="false">)</mml:mo> </mml:math> <jats:inline-graphic xmlns:xlink="" xlink:href="apjacc06eieqn1.gif" xlink:type="simple" /> </jats:inline-formula> as traced by 21 cm in current surveys. Using the column density structure of the neutral gas and stellar line-of-sight depths as a guide, we estimate the upper limit mass of the ionized component of the LMC to be roughly jats:italicM</jats:italic> jats:subionized</jats:sub> ≈ (0.6–1.8) × 10jats:sup9</jats:sup> jats:italicM</jats:italic> jats:sub☉</jats:sub>, which is comparable to the total neutral atomic gas mass in the same region (jats:italicM</jats:italic> jats:subneutral</jats:sub> ≈ 0.76–0.85 × 10jats:sup9</jats:sup> jats:italicM</jats:italic> jats:sub☉</jats:sub>). Considering only the atomic phases, we find jats:italicM</jats:italic> jats:subionized</jats:sub>/jats:italicM</jats:italic> jats:subionized+neutral</jats:sub>, to be 46%–68% throughout the LMC and its extended halo. Additionally, we find an ionized gas cloud that extends off of the LMC at (jats:italicℓ</jats:italic>, jats:italicb</jats:italic>) ≈ (285°, − 28°) into a region previously identified as the Leading Arm complex. This gas is moving at a similar line-of-sight velocity as the LMC and has jats:italicM</jats:italic> jats:subionized</jats:sub>/jats:italicM</jats:italic> jats:subionized+neutral</jats:sub> = 13%–51%. This study, combined with previous studies of the SMC and extended structures of the Magellanic Clouds, continues to suggest that warm, ionized gas is as massive and dynamically important as the neutral gas in the Magellanic System.</jats:p>



5101 Astronomical Sciences, 51 Physical Sciences

Journal Title

The Astrophysical Journal

Conference Name

Journal ISSN


Volume Title


American Astronomical Society
National Science Foundation (NSF) (1108911, 1714472/171562, 20092763)
National Science Foundation (NSF) (AST-2102490)