A study of stellar population of intermediate-age globular cluster NGC 2249

Zhongmu Li; Rainer Spurzem; Caiyan Mao; Yingxin Ma; Yangyang Deng

Results in Physics (Jun 2020)

A study of stellar population of intermediate-age globular cluster NGC 2249

Zhongmu Li,
Rainer Spurzem,
Caiyan Mao,
Yingxin Ma,
Yangyang Deng

Affiliations

Zhongmu Li: Institute for Astronomy and History of Science and Technology, Dali University, Dali 671003, China; Corresponding author.
Rainer Spurzem: Zentrum für Astronomie – Astronomisches Rechen-Institut, Mönchhofstr. 12-14, 69120 Heidelberg, Germany; Key Lab for Computational Astrophysic, National Astronomical Observatories of China, Chinese Academy of Sciences NAOC/CAS, 20A Datun Rd., Chaoyang District, Beijing 100012, China; Kavli Institute for Astronomy and Astrophysics, Peking University, 5 Yi He Yuan Rd. 5, Haidian District, Beijing 100871, China
Caiyan Mao: Institute for Astronomy and History of Science and Technology, Dali University, Dali 671003, China
Yingxin Ma: Institute for Astronomy and History of Science and Technology, Dali University, Dali 671003, China; Shanghai Key Lab for Astrophysics, Shanghai Normal University, Shanghai 200234, China
Yangyang Deng: Institute for Astronomy and History of Science and Technology, Dali University, Dali 671003, China; Shanghai Key Lab for Astrophysics, Shanghai Normal University, Shanghai 200234, China

Journal volume & issue: Vol. 17
p. 103144

Abstract

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The Large Magellanic Cloud (LMC) star cluster NGC 2249 has been found to exhibit an extended main-sequence turn-off (eMSTO) in the color-magnitude diagram (CMD) derived from the data of the Hubble Space Telescope (HST). Such CMDs can potentially be explained via a spread of stellar age or rotation rate of single-aged stars, leading to a confusion of its stellar population type. In this work, we use different combinations of age spread (A), rotation (R), and binarity (B) to study the stellar population of this cluster, via a deep HST CMD. Because binaries are commonly observed in star clusters, three models of this study take binaries into account. We finally derive the best-fit stellar population parameters, i.e., metallicity (Z = 0.008), age (0.7–1.0Gyr), reddening (E(B-I) = 0.52–0.55 mag), distance modulus (18.54–18.57mag), binary fraction (50%), rotating star fraction (0–50%), and star formation history mode for NGC 2249. We find that both age spread (A + B or A + R + B) and rotating stars (R + B) can reproduce the main CMD features well, while rotation alone does not reproduce the detailed eMSTO morphology. This suggests that an age spread of 200Myrs is needed to form the eMSTO of cluster NGC 2249, even if stellar rotation is taken into account. Dynamical simulation could be useful for revealing the origin of the eMSTO.

Published in Results in Physics

ISSN: 2211-3797 (Online)
Publisher: Elsevier
Country of publisher: Netherlands
LCC subjects: Science: Physics
Website: http://www.journals.elsevier.com/results-in-physics/

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