Scylla. III. The Outside-in Radial Age Gradient in the Small Magellanic Cloud and the Star Formation Histories of the Main Body, Wing, and Outer Regions

Roger E. Cohen; Kristen B. W. McQuinn; Claire E. Murray; Benjamin F. Williams; Yumi Choi; Christina W. Lindberg; Clare Burhenne; Karl D. Gordon; Petia Yanchulova Merica-Jones; Caroline Bot; Andrew E. Dolphin; Karoline M. Gilbert; Steven Goldman; Alec S. Hirschauer; Karin M. Sandstrom; O. Grace Telford

doi:10.3847/1538-4357/ad76a6

The Astrophysical Journal (Jan 2024)

Scylla. III. The Outside-in Radial Age Gradient in the Small Magellanic Cloud and the Star Formation Histories of the Main Body, Wing, and Outer Regions

Roger E. Cohen,
Kristen B. W. McQuinn,
Claire E. Murray,
Benjamin F. Williams,
Yumi Choi,
Christina W. Lindberg,
Clare Burhenne,
Karl D. Gordon,
Petia Yanchulova Merica-Jones,
Caroline Bot,
Andrew E. Dolphin,
Karoline M. Gilbert,
Steven Goldman,
Alec S. Hirschauer,
Karin M. Sandstrom,
O. Grace Telford

Affiliations

Roger E. Cohen: ORCiD; Department of Physics and Astronomy, Rutgers, The State University of New Jersey , 136 Frelinghuysen Road, Piscataway, NJ 08854, USA ; [email protected]
Kristen B. W. McQuinn: ORCiD; Department of Physics and Astronomy, Rutgers, The State University of New Jersey , 136 Frelinghuysen Road, Piscataway, NJ 08854, USA ; [email protected]; Space Telescope Science Institute , 3700 San Martin Drive, Baltimore, MD 21218, USA
Claire E. Murray: ORCiD; Space Telescope Science Institute , 3700 San Martin Drive, Baltimore, MD 21218, USA; The William H. Miller III Department of Physics & Astronomy, Bloomberg Center for Physics and Astronomy, Johns Hopkins University , 3400 N. Charles Street, Baltimore, MD 21218, USA
Benjamin F. Williams: ORCiD; Department of Astronomy, University of Washington , Box 351580, U. W., Seattle, WA 98195-1580, USA
Yumi Choi: ORCiD; NSF National Optical-Infrared Astronomy Research Laboratory , 950 N. Cherry Avenue, Tucson, AZ 85719, USA
Christina W. Lindberg: ORCiD; Space Telescope Science Institute , 3700 San Martin Drive, Baltimore, MD 21218, USA; The William H. Miller III Department of Physics & Astronomy, Bloomberg Center for Physics and Astronomy, Johns Hopkins University , 3400 N. Charles Street, Baltimore, MD 21218, USA
Clare Burhenne: ORCiD; Department of Physics and Astronomy, Rutgers, The State University of New Jersey , 136 Frelinghuysen Road, Piscataway, NJ 08854, USA ; [email protected]
Karl D. Gordon: ORCiD; Space Telescope Science Institute , 3700 San Martin Drive, Baltimore, MD 21218, USA
Petia Yanchulova Merica-Jones: Space Telescope Science Institute , 3700 San Martin Drive, Baltimore, MD 21218, USA
Caroline Bot: ORCiD; Observatoire Astronomique de Strasbourg, Université de Strasbourg , UMR 7550, 11 rue de l’Université, F-67000 Strasbourg, France
Andrew E. Dolphin: ORCiD; Raytheon , 1151 E. Hermans Road, Tucson, AZ 85756, USA; University of Arizona , Steward Observatory, 933 North Cherry Avenue, Tucson, AZ 85721, USA
Karoline M. Gilbert: ORCiD; Space Telescope Science Institute , 3700 San Martin Drive, Baltimore, MD 21218, USA; The William H. Miller III Department of Physics & Astronomy, Bloomberg Center for Physics and Astronomy, Johns Hopkins University , 3400 N. Charles Street, Baltimore, MD 21218, USA
Steven Goldman: ORCiD; Space Telescope Science Institute , 3700 San Martin Drive, Baltimore, MD 21218, USA
Alec S. Hirschauer: ORCiD; Space Telescope Science Institute , 3700 San Martin Drive, Baltimore, MD 21218, USA
Karin M. Sandstrom: ORCiD; Department of Astronomy & Astrophysics, University of California San Diego , 9500 Gilman Drive, La Jolla, CA 92093, USA
O. Grace Telford: ORCiD; Department of Physics and Astronomy, Rutgers, The State University of New Jersey , 136 Frelinghuysen Road, Piscataway, NJ 08854, USA ; [email protected]; Department of Astrophysical Sciences, Princeton University , 4 Ivy Lane, Princeton, NJ 08544, USA; The Observatories of the Carnegie Institution for Science , 813 Santa Barbara Street, Pasadena, CA 91101, USA

DOI: https://doi.org/10.3847/1538-4357/ad76a6
Journal volume & issue: Vol. 975, no. 1
p. 43

Abstract

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The proximity of the Large and Small Magellanic Clouds (LMC and SMC) provides the opportunity to study the impact of dwarf–dwarf interactions on their mass assembly with a unique level of detail. To this end, we analyze two-filter broadband imaging of 83 Hubble Space Telescope (HST) pointings covering 0.203 deg ^2 toward the SMC, extending out to ∼3.5 kpc in projection from its optical center. Lifetime star formation histories (SFHs) fit to each pointing independently reveal an outside-in age gradient such that fields in the SMC outskirts are older on average. We measure radial gradients of the look-back time to form 90%, 75%, and 50% of the cumulative stellar mass for the first time, finding δ ( τ _90 , τ _75 , τ _50 )/ δ R = (0.61 ${}_{-0.07}^{+0.08}$ , ${0.65}_{-0.08}^{+0.09}$ , ${0.82}_{-0.16}^{+0.12}$ ) Gyr kpc ^−1 assuming PARSEC evolutionary models and a commonly used elliptical geometry of the SMC, although our results are robust to these assumptions. The wing of the SMC deviates from this trend, forming 25% of its cumulative mass over the most recent 3 Gyr owing to a best-fit star formation rate that remains approximately constant. Our results are consistent with chemodynamical evidence of a tidally stripped SMC component in the foreground and imply contributions to the observed SFH from multiple previous LMC–SMC interactions. We also compare our SMC SFH with results from a companion study of the LMC, finding that while the two galaxies present different internal, spatially resolved SFH trends, both the LMC and SMC have similar near-constant lifetime SFHs when viewed globally.

Published in The Astrophysical Journal

ISSN: 1538-4357 (Online)
Publisher: IOP Publishing
Country of publisher: United Kingdom
LCC subjects: Science: Astronomy: Astrophysics
Website: https://iopscience.iop.org/journal/0004-637X

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