| 其他摘要 | Star clusters are powerful tools for examining stellar evolution models and studying the structure and evolution of galaxies. As the basic component of the Milky Way, star clusters are roughly divided into globular clusters and open clusters, which are mainly distributed in the Galactic halo and disk respectively. The distribution determines the crucial role of star clusters in the study of the structure, formation, and evolution of the Milky Way. Stellar population property is a key feature for the Galactic clusters, i.e., Age, metallicity, distance, color excess, special stars, spatial distribution, star formation history, and stellar kinematics, etc. The study of stellar population properties of Galactic clusters can effectively limit the structure and evolution models of the Milky Way, promote our understanding of Galactic clusters and the Milky Way, and help us investigate the mechanisms and evolutionary pathways of star formation in clusters. Therefore, the property of star clusters in the Milky Way is an important field in astronomy. In recent years, with the release of high-quality observational data such as HST, Gaia, and LAMOST, many works have used astrometric data, such as magnitude, coordinates, proper motion, and parallax, as well as and photometric and accurate spectroscopic data, to search for and identify Galactic clusters and study the properties of galaxy clusters, continuously expanding and improving the catalog of Galactic clusters. The results of stellar population properties obtained from different stellar population models and data are different. The properties need to be studied more systematically and in-depth. Therefore, this work studies the properties of star clusters in the Milky Way from three aspects.Firstly, this work uses Gaia EDR3 data and the Powerful CMD code to obtain basic parameters (age, metallicity, color excess, distance modulus, binary and rotating star fractions) and the distributions of 655 Galactic disk clusters (61 in which are newly discovered) located in the low latitude region (b<25°), by taking binaries, rotating stars, and age spread into account. The result shows that the age range of these 655 Galactic disk clusters is within 2.5 Gyr, with a metallicity range of 0.0001-0.03. Most clusters contain binary stars, and the binary fractions are mainly distributed between 0.30 and 0.55. Some clusters include extended main-sequence turnoff (eMSTO) structures in color-magnitude diagrams (CMDs), which could be reproduced by stellar rotation or multiple starbursts. All the results are summarized in a catalog called, LISC.Secondly, this work redetermines the 79 Galactic disk clusters in LISC catalog using low- and medium-resolution stellar spectral data, because the cluster metallicities in LISC catalog are mainly distributed within the range of Z<0.01. The newly obtained metallicities are compared with results from other surveys. We also compare the isochrones of different stellar evolution models and analyze the uncertainties in CMD fitting process. The stellar population parameters of these clusters are also redetermined by fixing the metallicities as the newly obtained ones. The results indicate that the metallicities obtained from LAMOST show a linear relation with those from LISC, i.e., [Fe/H]spec=-0.0061(±0.0481)[Fe/H]cmd -0.1598(±0.0512). The smaller metallicity values in the LISC catalog are mainly caused by the stellar evolution model used in Powerful CMD code, along with differences in atmospheric models and errors in the fitting process. The metallicity affects the determination of cluster age as well. In terms of the fitting results of CMDs of star clusters, smaller metallicities will lead to a larger age.Finally, we apply Powerful CMD code and PARSEC isochrones simultaneously to study the stellar population types and the reasons for eMSTO structures of Galactic star clusters. The stellar populations of 20 new star clusters and 6 known star clusters that have not been found to contain eMSTOs are classified and then fitted. Among them, the fitting results of 11 star clusters are very reliable. The results show that the stellar population types of 6 clusters are multiple stellar populations, and the other 5 clusters include simple stellar populations with stellar rotation. The combination of binary and stellar rotation is the main reason for eMSTOs in most star clusters, while age spread leads to better fitting results of the three clusters. Therefore, the effect of age spread on reproducing eMSTOs can not be ignored, especially in very young clusters (≤0.6 Gyr).The work applies Advanced Stellar Population Synthesis model and stellar spectral parameter to obtain stellar population parameters of the Galactic clusters. The results are helpful for future research on the formation and evolution of star clusters, galaxies, and stars. |
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