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A Galactic Eclipse: The Small Magellanic Cloud Is Forming Stars in Two Superimposed Systems

Murray, Claire E.; Hasselquist, Sten; Peek, Joshua E. G.; Lindberg, Christina Willecke; Almeida, Andres; Choi, Yumi; Craig, Jessica E. M.; Dénes, Helga; Dickey, John M.; Di Teodoro, Enrico M.; Federrath, Christoph; Gerrard, Isabella. A.; Gibson, Steven J.; Leahy, Denis; Lee, Min-Young; Lynn, Callum; Ma, Yik Ki; Marchal, Antoine; McClure-Griffiths, N. M.; Nidever, David; Nguyen, Hiep; Pingel, Nickolas M.; Tarantino, Elizabeth; Uscanga, Lucero; van Loon, Jacco Th.


Claire E. Murray

Sten Hasselquist

Joshua E. G. Peek

Christina Willecke Lindberg

Andres Almeida

Yumi Choi

Jessica E. M. Craig

Helga Dénes

John M. Dickey

Enrico M. Di Teodoro

Christoph Federrath

Isabella. A. Gerrard

Steven J. Gibson

Denis Leahy

Min-Young Lee

Callum Lynn

Yik Ki Ma

Antoine Marchal

N. M. McClure-Griffiths

David Nidever

Hiep Nguyen

Nickolas M. Pingel

Elizabeth Tarantino

Lucero Uscanga


The structure and dynamics of the star-forming disk of the Small Magellanic Cloud (SMC) have long confounded us. The SMC is widely used as a prototype for galactic physics at low metallicity, and yet we fundamentally lack an understanding of the structure of its interstellar medium (ISM). In this work, we present a new model for the SMC by comparing the kinematics of young, massive stars with the structure of the ISM traced by high-resolution observations of neutral atomic hydrogen (H i) from the Galactic Australian Square Kilometre Array Pathfinder survey. Specifically, we identify thousands of young, massive stars with precise radial velocity constraints from the Gaia and APOGEE surveys and match these stars to the ISM structures in which they likely formed. By comparing the average dust extinction toward these stars, we find evidence that the SMC is composed of two structures with distinct stellar and gaseous chemical compositions. We construct a simple model that successfully reproduces the observations and shows that the ISM of the SMC is arranged into two superimposed, star-forming systems with similar gas mass separated by ∼5 kpc along the line of sight.


Murray, C. E., Hasselquist, S., Peek, J. E. G., Lindberg, C. W., Almeida, A., Choi, Y., …van Loon, J. T. (2024). A Galactic Eclipse: The Small Magellanic Cloud Is Forming Stars in Two Superimposed Systems. Astrophysical Journal, 962(2), Article 120.

Journal Article Type Article
Acceptance Date Dec 12, 2023
Online Publication Date Feb 13, 2024
Publication Date Feb 1, 2024
Deposit Date Feb 20, 2024
Journal The Astrophysical Journal
Print ISSN 0004-637X
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 962
Issue 2
Article Number 120
Keywords Interstellar medium, Galaxy structure, Radio astronomy, Small Magellanic Cloud, Dwarf galaxies, Chemical abundances
Publisher URL