星系金属丰度的研究进展(Ⅰ):定标方法

The Methods and Study Progress About Estimating Metallicities of Galaxies(I): Calibration Methods

金属丰度是表征星系特征的重要参量,对于理解星系的形成与演化具有重要意义。随着观测设备的不断完善与发展,已经获得越来越多的星系(包括近邻星系、中等红移及高红移星系)金属丰度的观测资料。在光致电离模型方面也取得了很大进展．这些对于理解星系中金属及恒星成分的累积历史有非常重要的作用。有多种方法可以用来估计星系的金属丰度(主要是星际介质中气相的O丰度),介绍和评述了估计星系的O丰度的多种方法,包括电子温度的方法、R23方法以及其他一些“强线”比值的方法,并给出了相应的解析公式,同时介绍了电离星云的物理本质及由光致电离模型估计星系金属丰度的方法,还给出了估计星系的C和N元素丰度的方法。

Metallicity is a fundamental parameter to trace the formation and evolution of galaxies. With the developed observational ability and facilities, the metallicities of more and more galaxies were obtained, from the local dwarfs and spirals to the star-forming galaxies in the intermediate redshift Universe, and even to the high redshift Lyman Break Galaxies （LBGs）. Moreover, the corresponding photoionization models have been developed a lot. These can help well to understand the assembly history of stellar masses and metals of galaxies. We review the many methods used to estimate the gas-phase oxygen abundances of the interstellar medium of galaxies in this paper, including the Te-method, the R23 method, and other ＂strong-line-ratio＂ methods, and then give the related analytic fitting formulas. We also introduce the physical properties of ionized nebulae, and the methods using photoionization models to estimate metallicities of galaxies. Finally, we review the methods to estimate C and N abundances of galaxies.