High spectral resolution evolutionary synthesis models have become a routinely used ingredient in extragalactic work, and as such deserve thorough testing. Star clusters are ideal laboratories for such tests. This paper applies the spectral fitting methodology outlined in Paper I to a sample of clusters, mainly from the Magellanic Clouds and spanning a wide range in age and metallicity, fitting their integrated light spectra with a suite of modern evolutionary synthesis models for single stellar population. The combinations of model plus spectral library employed in this investigation are Galaxev/STELIB, Vazdekis/MILES, SED@/GRANADA, and Galaxev/MILES+GRANADA, which provide a representative sample of models currently available for spectral fitting work. A series of empirical tests are performed with these models, comparing the quality of the spectral fits and the values of age, metallicity and extinction obtained with each of them. A comparison is also made between the properties derived from these spectral fits and literature data on these nearby, well studied clusters. These comparisons are done with the general goal of providing useful feedback for model makers, as well as guidance to the users of such models. We find that new generation of models using the GRANADA and MILES libraries are superior to STELIB-based models both in terms of spectral fit quality and regarding the accuracy with which age and metallicity are retrieved. Accuracies of about 0.1 dex in age and 0.3 dex in metallicity can be achieved as long as the models are not extrapolated beyond their expected range of validity.
The stellar populations of early-type galaxies -- I. Observations, line-strengths and stellar population parameters
环境对早型星系形成和演化的影响是一个尚未解决的问题。通过考察早期星系的恒星星族作为环境的函数,可以对早期星系形成和演化的模型加以限制。我们提出了一个非常适合这种调查的星系目录。星等限制(bJ <19.45)样本取自四个星团(后发座、A1139、A3558和A930 at <z>=0.04)及其周围。该星表包含416个星系的光度、红移、速度色散和Lick线强度,其中245个被归类为早期类型。亮度加权年龄,金属丰度和α元素丰度比已估计为219这些早期类型。我们还概述了测量完全校准的利克指数和估计相关的恒星星族参数使用最新的方法和恒星星族模型的必要步骤。在随后的论文中,我们对星团中早型星系的恒星星族进行了详细的研究,并探讨了环境的影响。
这是我在2011年IAC在Puerto de la Cruz冬季学校的演讲摘要。本文介绍了星系中恒星星族的研究现状,并着重介绍了一些新的结果。由于冬季学校的标题是{ \it银河系的长期演化},我主要集中在附近的星系,这是最适合研究这个主题。当然,对恒星星族的理解与对星系形成和演化的理解密切相关,而星系形成和演化是天文学最大的突出问题之一。我们目前所处的情况是,近年来在观测方面取得了非常大的进展。已探测到红移高达10的星系。必须付出巨大的努力,使恒星星族理论能够赶上观测。由于大多数星系都很遥远,关于它们的信息必须来自于恒星星族综合光的合成。在这里,我将讨论如何恒星演化理论,连同我们的银河系和本星系群的观测,作为积木来分析这些综合恒星星族。
The stellar populations of massive galaxies in the local Universe
我简要回顾了大质量星系的恒星星族特性,特别关注早期类型星系,重点是ATLAS 3D Survey的最新结果。我讨论的年轻恒星年龄的发生,冷气体,并正在进行的早期型星系的恒星形成,这些星系的演化路径的存在提供了重要的线索。考虑经验恒星形成的历史给出了一个有意义的图片星系恒星星族属性,并允许人口和动力学的质量估计进行准确的比较。这一点最近为国际货币基金组织的非普遍性提供了有力的证据,最近的其他证据也支持这一点。对恒星星族的空间分辨研究对于将星系内不同的组成部分与其他波长或参数下看到的空间结构联系起来也至关重要。对于观测者来说,早期类型星系暗淡外层包层中的恒星星族是一个令人生畏的前沿,但它有望限制吸积恒星质量与“原位”形成的恒星质量的比率--这是最近星系形成模型的一个关键特征。星系环境似乎在控制低质量星系的恒星星族性质方面起着关键作用。然而,模拟提醒我们,当今的星系是复杂的组装和环境历史的产物,这引起了我们所看到的趋势。这对我们对环境趋势的解释有很大的影响。