Comparisons of different fitting methods for the physical parameters of a star cluster sample of m33 with spectroscopy and photometry

Zhou Fan*, Bingqiu Chen, Xiaoying Pang, Juanjuan Ren, Song Wang, Jing Wang, Kefeng Tan, Nan Song, Chun Li, Jie Zheng, Gang Zhao

*Corresponding author for this work

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1 Citation (Scopus)


Star clusters are good tracers for formation and evolution of galaxies. We compared different fitting methods by using spectra (or by combining photometry) to determine the physical parameters. We choose a sample of 17 star clusters in M33, which previously lacked spectroscopic observations. The low-resolution spectra were taken with the Xinglong 2.16 m reflector of NAOC. The photometry used in the fitting includes uSC and vSAGE bands from the SAGE survey, as well as the published UBVRI and ugriz photometry. We first derived ages and metallicities with the ULYSS (Vazdekis et al. and PEGASE-HR) simple stellar population model and the Bruzual & Charlot stellar population synthesis models for the full-spectrum fitting. The fitting results of both the BC03 and ULYSS models seem consistent with those of previous works as well. Then, we add the SAGE uSC and vSAGE photometry in the spectroscopic fitting with the BC03 models. It seems that the results become much better, especially for the Padova 2000+Chabrier initial mass function set. Finally, we add more photometry data, UBVRI and ugriz, in the fitting, and we found that the results do not improve significantly. Therefore, we conclude that the photometry is useful for improving the fitting results, especially for the blue bands (λ < 4000 Å), e.g., uSC and vSAGE band. At last, we discuss the "UV excess"for the star clusters, and we find that five star clusters have UV excess, based on the GALEX far-UV and near-UV photometry.

Original languageEnglish
Article numberabb700
JournalAstrophysical Journal, Supplement Series
Issue number1
Publication statusPublished - Nov 2020

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