基于LAMOST恒星光谱的视向速度精度问题的研究

发布时间：2018-04-13 20:10

本文选题：低分辨率 + 视向速度　；参考：《北京化工大学》2011年硕士论文

【摘要】：在多普勒效应的影响下,恒星光谱的谱线会发生移动,通过测量这些谱线的移动就能得到恒星的视向速度。一旦获得大量的恒星的视向速度,就可用于研究银河系的运动学和恒星的演化等。 LAMOST是一台高效率的天文望远镜,每次观测能同时对准4000个目标,每个观测夜能获得1～2万个目标光谱。面对这样的海量数据,视向速度的测量可以采用多种算法自动进行。本文通过模拟LAMOST光谱的方式,对目前拟采用的交叉相关算法在各种条件下的运算精度进行分析,研究了各因素对视向速度精度测量的影响。通过本文工作,可以对将来发布数据的测量结果进行评价,给出置信区间和精度,为LAMOST的科学产出提供可靠的数据处理的保证。本文的主要工作有以下几个方面： (1)对于不同温度下不同类型的恒星光谱,通过理论光谱的模拟和统计分析,检验了计算视向速度时,交叉相关算法本身以及由于仪器的最小分辨率和数据采样率等多种因素带来的误差。结果证实了选择交叉相关是比较可靠且精度较高的算法。 (2)光谱在波长定标过程中带来误差的原因是复杂的,有仪器的非线性原因、拟合灯谱发射线位置的误差、拟合色散曲线带来的误差等等。这些因素综合起来,在LAMOST的实际光谱定标时,会产生7km/s左右的零点误差和15km/s左右的随机误差,本文对此进行了模拟分析。 (3) LAMOST仪器的效率是随波长变化的,观测得到的光谱往往叠加了其固有的效率曲线。对于LAMOST效率曲线在计算视向速度时的影响,在本文工作中也进行了仿真,并给出了分析结论。 (4)算法对噪声的敏感程度,决定了视向速度的可靠性。我们将光谱叠加了按照LAMOST噪声模型产生的随机噪声,构造出与LAMOST实际观测得到的光谱相似的光谱。经过大数据量的模拟,统计出信噪比降低与视向速度误差增大的关系。
[Abstract]:Under the influence of Doppler effect, the spectral lines of the star will move, and the apparent velocity of the star can be obtained by measuring the movement of these spectral lines.Once the apparent velocities of a large number of stars are obtained, they can be used to study the kinematics and stellar evolution of the Milky way.LAMOST is an efficient telescope, which can aim at 4,000 targets at the same time, and obtain 10-20,000 target spectra per observation night.In the face of such massive data, the measurement of apparent velocity can be carried out automatically by a variety of algorithms.In this paper, by simulating the LAMOST spectrum, the computational accuracy of the cross-correlation algorithm is analyzed under various conditions, and the influence of various factors on the measurement of apparent velocity accuracy is studied.Through the work of this paper, we can evaluate the measurement results of the published data in the future, give the confidence interval and precision, and provide reliable data processing guarantee for the scientific output of LAMOST.The main work of this paper is as follows:1) for different types of star spectra at different temperatures, the calculation of apparent velocities is tested by simulation and statistical analysis of theoretical spectra.The cross-correlation algorithm itself and the error caused by the minimum resolution and data sampling rate of the instrument.The results show that selecting cross correlation is a reliable and accurate algorithm.(2) the causes of spectrum error in wavelength calibration are complex, the nonlinear reason of instrument, the position error of fitting lamp spectrum emission line, the error caused by fitting dispersion curve and so on.When these factors are combined, the zero error of 7km/s and the random error of 15km/s will be produced in the actual spectral calibration of LAMOST.The efficiency of the LAMOST instrument varies with the wavelength, and the observed spectra often superimpose its inherent efficiency curve.The effect of LAMOST efficiency curve on calculating apparent velocity is also simulated in this paper, and the analysis results are given.The sensitivity of the algorithm to noise determines the reliability of apparent velocity.The spectrum is superimposed on the random noise generated by the LAMOST noise model, and a spectrum similar to the spectrum observed by LAMOST is constructed.The relation between the decrease of signal-to-noise ratio and the increase of apparent velocity error is obtained through the simulation of large amount of data.
【学位授予单位】：北京化工大学
【学位级别】：硕士
【学位授予年份】：2011
【分类号】：P141.5

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