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.

Abstract

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.

Citation

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. https://doi.org/10.3847/1538-4357/ad1591

• 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
• DOI: https://doi.org/10.3847/1538-4357/ad1591
• Keywords: Interstellar medium, Galaxy structure, Radio astronomy, Small Magellanic Cloud, Dwarf galaxies, Chemical abundances
• Publisher URL: https://iopscience.iop.org/article/10.3847/1538-4357/ad1591