TY - JOUR
T1 - Multiple stellar populations at less-evolved stages
T2 - detection of chemical variations among main-sequence dwarfs in NGC 1978
AU - Li, Chengyuan
AU - Tang, Baitian
AU - Milone, Antonino P.
AU - de Grijs, Richard
AU - Hong, Jongsuk
AU - Yang, Yujiao
AU - Wang, Yue
N1 - Copyright © 2021. The American Astronomical Society. First published in the Astrophysical Journal, 906(2), 50, 2021, published by IOP Publishing. The original publication is available at https://doi.org/10.3847/1538-4357/abc8f2. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.
PY - 2021/1/18
Y1 - 2021/1/18
N2 - Multiple stellar populations (MPs) with different chemical compositions are not exclusive features of old globular clusters (older than 10 Gyr). Indeed, recent studies reveal that younger clusters (~2–6 Gyr-old) in the Magellanic Clouds also exhibit star-to-star chemical variations among evolved stars. However, whether MPs are present among less-evolved dwarfs of these intermediate-age clusters is still unclear. In this work, we search for chemical variations among GK-type dwarfs in the ~2 Gyr old cluster NGC 1978, which is the youngest cluster with MPs. We exploit deep ultraviolet and visual observations from the Hubble Space Telescope to constrain the nitrogen (N) and oxygen (O) variations among main-sequence (MS) stars. To do this, we compare appropriate photometric diagrams that are sensitive to N and O with synthetic diagrams of simple stellar populations and MPs. We conclude that the G- and K-type MS stars in NGC 1978 host MPs. Our statistical analysis shows that the fraction of N-rich stars ranges from ~40% to ~80%, depending on the detailed distributions of N and O.
AB - Multiple stellar populations (MPs) with different chemical compositions are not exclusive features of old globular clusters (older than 10 Gyr). Indeed, recent studies reveal that younger clusters (~2–6 Gyr-old) in the Magellanic Clouds also exhibit star-to-star chemical variations among evolved stars. However, whether MPs are present among less-evolved dwarfs of these intermediate-age clusters is still unclear. In this work, we search for chemical variations among GK-type dwarfs in the ~2 Gyr old cluster NGC 1978, which is the youngest cluster with MPs. We exploit deep ultraviolet and visual observations from the Hubble Space Telescope to constrain the nitrogen (N) and oxygen (O) variations among main-sequence (MS) stars. To do this, we compare appropriate photometric diagrams that are sensitive to N and O with synthetic diagrams of simple stellar populations and MPs. We conclude that the G- and K-type MS stars in NGC 1978 host MPs. Our statistical analysis shows that the fraction of N-rich stars ranges from ~40% to ~80%, depending on the detailed distributions of N and O.
UR - http://www.scopus.com/inward/record.url?scp=85100303198&partnerID=8YFLogxK
U2 - 10.3847/1538-4357/abc8f2
DO - 10.3847/1538-4357/abc8f2
M3 - Article
SN - 0004-637X
VL - 906
SP - 1
EP - 13
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2
M1 - 133
ER -