Semi‐empirical analysis of Sloan Digital Sky Survey galaxies – I. Spectral synthesis method
Semi‐empirical analysis of Sloan Digital Sky Survey galaxies – I. Spectral synthesis method
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DOI：
10.1111/j.1365-2966.2005.08752.x
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发表时间：
2005-04
影响因子：
4.8
通讯作者：
R. C. Fernandes;A. Mateus;L. Sodré;G. Stasińska;J. Gomes
中科院分区：
文献类型：
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作者：
R. C. Fernandes;A. Mateus;L. Sodré;G. Stasińska;J. Gomes
随着观测到的星系光谱和最先进的演化综合模型的大型高质量数据库的可用性，星系中恒星种群的研究正在进入一个新时代。在本文中，我们研究了光谱合成作为估计星系物理特性的一种手段的力量。光谱合成只不过是根据不同年龄和金属丰度的简单恒星群的叠加来分解观测到的光谱，从而产生恒星形成和星系的化学历史、其灭绝和速度色散作为输出。我们对该方法的实施使用了 Bruzual 和 Charlot 的最新模型以及在 3650–8000 A 范围内观察到的光谱。该方法的可靠性通过三种不同的方式进行研究：（1）模拟，（2）与基于不同技术的先前工作进行比较，以及（3）对从斯隆数字巡天（SDSS）的星系样本获得的结果的一致性进行分析。我们发现，只要不尝试对恒星形成和化学历史进行非常详细的描述，光谱合成就可以提供可靠的物理参数。通过结合基础中每个简单恒星群的（个体不确定的）强度，可以获得稳健且物理上有趣的参数。特别是，我们表明，除了对观测到的星系光谱提供良好的拟合之外，该方法还能够恢复有关恒星年龄分布的有用信息，更重要的是，恢复有关恒星金属丰度的有用信息。还发现可以准确地检索恒星质量、速度色散和消光，以获得真实的信噪比。我们将这种合成方法应用于来自 SDSS 数据版本 2 的 50 362 个星系的体积有限样本，生成恒星种群属性的目录。还研究了发射线，在从观测到的星光光谱中减去计算出的星光光谱后进行测量。尽管分析方法存在很大差异，但与其他小组最近对这些星系的观测和物理性质的估计进行比较，显示出良好的定性和定量一致性。综合结果与独立量之间的一些经验和天体物理学上合理的相关性进一步增强了对本方法的信心。例如，我们报告了恒星和星云金属丰度、恒星和星云消光、平均恒星年龄和 Hα 和 4000-A 断裂的等效宽度之间以及恒星质量和速度色散之间存在很强的相关性。
The study of stellar populations in galaxies is entering a new era with the availability of large and high-quality data bases of both observed galactic spectra and state-of-the-art evolutionary synthesis models. In this paper we investigate the power of spectral synthesis as a means to estimate the physical properties of galaxies. Spectral synthesis is nothing more than the decomposition of an observed spectrum in terms of a superposition of a base of simple stellar populations of various ages and metallicities, producing as output the star formation and chemical histories of a galaxy, its extinction and velocity dispersion. Our implementation of this method uses the recent models of Bruzual & Charlot and observed spectra in the 3650–8000 A range. The reliability of this approach is studied by three different means: (1) simulations, (2) comparison with previous work based on a different technique, and (3) analysis of the consistency of results obtained for a sample of galaxies from the Sloan Digital Sky Survey (SDSS). We find that spectral synthesis provides reliable physical parameters as long as one does not attempt a very detailed description of the star formation and chemical histories. Robust and physically interesting parameters are obtained by combining the (individually uncertain) strengths of each simple stellar population in the base. In particular, we show that, besides providing excellent fits to observed galaxy spectra, this method is able to recover useful information on the distributions of stellar ages and, more importantly, stellar metallicities. Stellar masses, velocity dispersion and extinction are also found to be accurately retrieved for realistic signal-to-noise ratios. We apply this synthesis method to a volume-limited sample of 50 362 galaxies from the SDSS Data Release 2, producing a catalogue of stellar population properties. Emission lines are also studied, their measurement being performed after subtracting the computed starlight spectrum from the observed one. A comparison with recent estimates of both observed and physical properties of these galaxies obtained by other groups shows good qualitative and quantitative agreement, despite substantial differences in the methods of analysis. The confidence in the present method is further strengthened by several empirical and astrophysically reasonable correlations between synthesis results and independent quantities. For instance, we report the existence of strong correlations between stellar and nebular metallicities, stellar and nebular extinctions, mean stellar age and equivalent width of Hα and 4000-A break, and between stellar mass and velocity dispersion.