大样本恒星演化研究组知识库

通过星族合成方法发现:在星系参数拟合计算中,相比于单星星族,双星星族可以得到更大的年龄和更高的金属丰度,但双星如何影响星系演化仍不清楚.另外,对于早型星系存在的紫外超现象,目前存在两种主流的解释,一种是有年轻的星族形成,另一种是由双星星族中产生的高温天体引起,但具体哪一种形成机制仍不确定.计算了双星演化抛入星际介质的元素,结合星系化学演化模型和MAPPINGS III程序,研究了双星星族对早型星系气体冷却以及星系演化影响.结果显示,相比于单星演化,双星演化使得抛出的物质和金属丰度增加.另外,得到了早型星系紫外超两种机制下,抛入星际介质的各种元素丰度,发现一些元素的丰度比是不同的,这就意味着,这两种机制可以利用元素丰度比和平均金属丰度进一步认证.同时也计算了两种机制下星系的冷却函数,发现双星机制下的冷却更加有效. 

Compared with the evolutionary population synthesis (EPS) models without binary interactions, the derived stellar age and metallicity of galaxies of the EPS models with binary interactions are larger. But, we do not know how the galaxies evolve if considering binary interactions in the galaxy evolution models. For early-type galaxies with the UV-upturn phenomenon, there are two explanations: recent star formation (RSF) and binary interactions. In this study, we obtain the mass return fraction and yields for stellar populations with and without binary interactions. In combination with the galaxy chemical and photoionization models, we study the effect of binary interactions on the chemical evolution of early-type galaxies, the metallicity evolution for the early-type galaxies with UV-upturn phenomenon under the two popular mechanisms. We find that the inclusion of binary interactions can raise the ejected mass, metallicity, alpha element, and accelerate the gas cooling. These can reasonably explain the conclusions made via the EPS models. Moreover, we find that the gas cooling is more efficient under the UV-upturn formation mechanism by binary interactions than RSF, and the ratios of metallicity are different for the two mechanisms, which can be further used to distinguish these two mechanisms.