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Register a new userComparisons of Different Fitting Methods for the Physical Parameters of A Star Cluster Sample of M33 with Spectroscopy and Photometry
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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 $rm u_{SC}$ and $rm v_{SAGE}$ bands from the SAGE survey, as well as the published $UBVRI$ and $ugriz$ photometry. We firstly derived ages and metallicities with the {sc ULySS} (Vazdekis et al. and {sc pegase-hr}) SSP model and the Bruzual & Charlot (2003) (BC03) stellar population synthesis models for the full-spectrum fitting. The fitting results of both the BC03 and {sc ULySS} models seem consistent with those of previous works as well. Then we add the SAGE $rm u_{SC}$ and $rm v_{SAGE}$ photometry in the spectroscopic fitting with the BC03 models. It seems the results become much better, especially for the Padova 2000+Chabrier IMF 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 ($lambda <4000$ {AA}), e.g., $rm u_{SC}$ and $rm v_{SAGE}$ band. At last, we discuss the UV-excess for the star clusters and we find five star clusters have UV-excess, based on the $GALEX$ FUV, NUV photometry.
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