LAMOST恒星大气参数提取系统
发布时间：2018-10-16 15:48
【摘要】： 随着LAMOST银河系巡天计划的开展,每个观测夜将获得上万条恒星光谱。光谱蕴含着天体的重要信息,通过恒星光谱来得到恒星的大气物理参数是天文学中的一个基础工作,因此恒星光谱分析在天体研究中占有重要地位。通过恒星光谱快速、准确、自动的提取恒星大气物理参数是非常值得研究和探索的。本研究针对LAMOST的需求,设计、实现了一套恒星大气参数提取系统。主要研究工作如下： 1、针对LAMOST的观测光谱进行预处理,利用11条强吸收线的观测波长和实验室波长的对比,计算得到视向速度,对光谱进行视向速度校正；然后对光谱的蓝段(3850-6000 A)和红端(6000-9000 A)分别进行多项式拟合,然后再综合进行多项式拟合,提取全局连续谱；针对83条原子线和分子线进行谱线特征提取等。 2、利用网格模板匹配提取恒星大气参数。使用Kurucz模型生成覆盖网格节点的两套理论光谱模板,一套为包含g-r色指数和4400-5500 A的标准化光谱,一套只包含4400-5500 A的标准化光谱。定义观测光谱和理论模板光谱之间的距离,利用Nelder-Mead算法快速搜索极小值,利用最接近的理论光谱的参数作为观测光谱的恒星大气参数,最后利用蒙特卡洛模拟噪声的分布,得到恒星大气参数的误差。 3、使用PCA降维的恒星光谱数据作为输入,利用神经网络提取恒星大气参数。将光谱的红蓝端分别降到二十五维,作为神经网络的输入,三个恒星大气参数作为输出,中间隐藏节点为十个,构建三层神经网络。使用理论光谱和SLOAN光谱(使用SSPP测量参数)作为训练数据及测试数据,训练得到两套神经网络系统。 4、使用卡方最小化技术提取恒星大气参数。首先生成两套不同的理论光谱模板,定义观测光谱和理论光谱之间的卡方距离,为了减少计算量,利用半流量点技术来进行初始的温度估计,然后使用剪枝的多项式拟合技术得到最小值,求得有效温度,使用同样的步骤依次求得表面重力值和金属丰度值。第二套模板中使用第一套模板求得得有效温度,不过第二套模板将在以后的应用中计算alpha元素丰度。在本系统中,我们还实现了通过观测的g-r色指数和通过巴尔默(Blamer)线系的强度预测得到有效温度,最终使用了两个理论的有效温度估计和三个经验有效温度估计。 5、利用银河系中的球状星系团和疏散星团的金属丰度值对本系统的参数值准确性进行了评估,并使用其他望远镜观测的高分辨率光谱提取的参数作为真实值,对本系统中的金属丰度参数进行了校正,得到每个算法在不同区间的误差和弥散度,对结果进行了重新加权,获得了较好的准确性。
[Abstract]:With the launch of the LAMOST Galactic Sky Survey program, tens of thousands of star spectra will be obtained per observation night. Spectra contain important information of celestial bodies. It is a basic work in astronomy to obtain the atmospheric physical parameters of stars by stellar spectra, so star spectral analysis plays an important role in the study of celestial bodies. It is worth studying and exploring to extract the atmospheric physical parameters of stars quickly, accurately and automatically through star spectrum. In order to meet the requirements of LAMOST, a stellar atmospheric parameter extraction system is designed and implemented in this paper. The main research work is as follows: 1. The observation spectrum of LAMOST is pretreated, and the apparent velocity is calculated by comparing the observation wavelength of 11 strong absorption lines with the wavelength of laboratory, and the spectrum is corrected by apparent velocity. Then the blue region (3850-6000A) and the red end (6000-9000 A) of the spectrum are fitted by polynomial respectively, and then the global continuous spectrum is extracted by comprehensive polynomial fitting. For 83 atomic and molecular lines, the spectral line features are extracted, etc. 2. The atmospheric parameters of stars are extracted by mesh template matching. The Kurucz model is used to generate two sets of theoretical spectral templates covering the grid nodes, one set of standardized spectra containing g-r color index and 4400-5500A, and one set containing only 4400-5500A standardized spectra. The distance between the observed spectrum and the theoretical template spectrum is defined. The Nelder-Mead algorithm is used to quickly search the minimum, and the nearest theoretical spectrum parameters are used as the atmospheric parameters of the observed spectrum. Finally, Monte Carlo is used to simulate the distribution of noise. The errors of stellar atmospheric parameters are obtained. 3. The star atmospheric parameters are extracted by neural network using PCA reduced dimension star spectral data as input. The red and blue side of the spectrum is reduced to 25 dimension, which is used as the input of the neural network, three star atmospheric parameters as the output, and ten hidden nodes in the middle. The three-layer neural network is constructed. Using theoretical spectrum and SLOAN spectrum (using SSPP measurement parameters) as training data and test data, two sets of neural network systems are trained. 4. Chi-square minimization technique is used to extract stellar atmospheric parameters. First, two sets of different theoretical spectral templates are generated to define the chi-square distance between the observed spectrum and the theoretical spectrum. In order to reduce the computational complexity, the half-flow point technique is used to estimate the initial temperature. Then the pruning polynomial fitting technique is used to obtain the minimum value and the effective temperature, and the surface gravity value and the metal abundance value are obtained in turn by the same steps. The first set of templates is used to obtain the effective temperature in the second set of templates, but the second set of templates will be used to calculate the abundance of alpha elements in future applications. In this system, we also achieve the effective temperature obtained by the observed g-r color index and the strength prediction of the Balmer (Blamer) line system. Finally, two theories of effective temperature estimation and three empirical effective temperature estimates are used. 5. The accuracy of the system parameters is evaluated by using the metallic abundance values of the globular clusters and the open clusters in the Milky way. Using the parameters extracted from high-resolution spectra observed by other telescopes as real values, the parameters of metal abundance in this system are corrected, the errors and dispersion of each algorithm in different regions are obtained, and the results are reweighted. Good accuracy has been obtained.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2010
【分类号】：P144
本文编号：2274839
[Abstract]:With the launch of the LAMOST Galactic Sky Survey program, tens of thousands of star spectra will be obtained per observation night. Spectra contain important information of celestial bodies. It is a basic work in astronomy to obtain the atmospheric physical parameters of stars by stellar spectra, so star spectral analysis plays an important role in the study of celestial bodies. It is worth studying and exploring to extract the atmospheric physical parameters of stars quickly, accurately and automatically through star spectrum. In order to meet the requirements of LAMOST, a stellar atmospheric parameter extraction system is designed and implemented in this paper. The main research work is as follows: 1. The observation spectrum of LAMOST is pretreated, and the apparent velocity is calculated by comparing the observation wavelength of 11 strong absorption lines with the wavelength of laboratory, and the spectrum is corrected by apparent velocity. Then the blue region (3850-6000A) and the red end (6000-9000 A) of the spectrum are fitted by polynomial respectively, and then the global continuous spectrum is extracted by comprehensive polynomial fitting. For 83 atomic and molecular lines, the spectral line features are extracted, etc. 2. The atmospheric parameters of stars are extracted by mesh template matching. The Kurucz model is used to generate two sets of theoretical spectral templates covering the grid nodes, one set of standardized spectra containing g-r color index and 4400-5500A, and one set containing only 4400-5500A standardized spectra. The distance between the observed spectrum and the theoretical template spectrum is defined. The Nelder-Mead algorithm is used to quickly search the minimum, and the nearest theoretical spectrum parameters are used as the atmospheric parameters of the observed spectrum. Finally, Monte Carlo is used to simulate the distribution of noise. The errors of stellar atmospheric parameters are obtained. 3. The star atmospheric parameters are extracted by neural network using PCA reduced dimension star spectral data as input. The red and blue side of the spectrum is reduced to 25 dimension, which is used as the input of the neural network, three star atmospheric parameters as the output, and ten hidden nodes in the middle. The three-layer neural network is constructed. Using theoretical spectrum and SLOAN spectrum (using SSPP measurement parameters) as training data and test data, two sets of neural network systems are trained. 4. Chi-square minimization technique is used to extract stellar atmospheric parameters. First, two sets of different theoretical spectral templates are generated to define the chi-square distance between the observed spectrum and the theoretical spectrum. In order to reduce the computational complexity, the half-flow point technique is used to estimate the initial temperature. Then the pruning polynomial fitting technique is used to obtain the minimum value and the effective temperature, and the surface gravity value and the metal abundance value are obtained in turn by the same steps. The first set of templates is used to obtain the effective temperature in the second set of templates, but the second set of templates will be used to calculate the abundance of alpha elements in future applications. In this system, we also achieve the effective temperature obtained by the observed g-r color index and the strength prediction of the Balmer (Blamer) line system. Finally, two theories of effective temperature estimation and three empirical effective temperature estimates are used. 5. The accuracy of the system parameters is evaluated by using the metallic abundance values of the globular clusters and the open clusters in the Milky way. Using the parameters extracted from high-resolution spectra observed by other telescopes as real values, the parameters of metal abundance in this system are corrected, the errors and dispersion of each algorithm in different regions are obtained, and the results are reweighted. Good accuracy has been obtained.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2010
【分类号】：P144
【引证文献】
相关硕士学位论文 前3条
1 杨琳;基于数据挖掘技术的激变变星的特征提取[D];山东大学;2011年
2 韦鹏;LAMOST一维光谱自动处理[D];山东大学;2011年
3 张周周;基于Matlab和VRML的虚拟销盘摩擦实验系统仿真设计[D];延边大学;2012年
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