星系NGC5018的星族合成研究

Population Synthesis for the Spectrum of NGC5018

利用星团谱样本的星族合成方法,研究了邻近巨椭圆星系NGC5018中的星族成分和其内部的恒星形成历史,给出了星系中不同年龄和金属丰度星族的成分占有比.星族合成结果表明,NGC5018中不仅存在大量金属丰度低的年老恒星成分,而且较年轻的星族成分(T=5×108yr)对星系光度贡献也很重要.星系吞并和相互作用过程可能是触发这些较年轻星族形成的物理原因,椭圆星系内部的恒星形成历史可能是2次爆发或者多次爆发过程.这些结果可以很好地解释NGC5018颜色偏蓝、Mg2谱指数强度偏弱等观测特征.

The long-slit spectral observations of NGC5018 in the range 3600-7500 A with the BAO 2.16m telescope are presented. Using the population synthesis method based on star cluster, the nuclear stellar population and star formation history of NGC5018 are analyzed. The results indicate that the continuum flux fraction at 5870 A owing to an old component is ~ 64%, and that of very young components (T<108yr)is<1%, respectively. A very interesting result is there exist lots of T=5x108yr young stellar populations in this old elliptical galaxy. It is supposed that the cause of the star formation is the influence of tidal interactions and minor mergers with other galaxies. The star formation history of the elliptical galaxies maybe very complex, but the results can give the observation characters of NGC5018 a good explanation.