本文選題：低分辨率 + 視向速度��； 參考：《北京化工大學(xué)》2011年碩士論文

【摘要】：在多普勒效應(yīng)的影響下,恒星光譜的譜線會發(fā)生移動,通過測量這些譜線的移動就能得到恒星的視向速度。一旦獲得大量的恒星的視向速度,就可用于研究銀河系的運動學(xué)和恒星的演化等。 LAMOST是一臺高效率的天文望遠(yuǎn)鏡,每次觀測能同時對準(zhǔn)4000個目標(biāo),每個觀測夜能獲得1～2萬個目標(biāo)光譜。面對這樣的海量數(shù)據(jù),視向速度的測量可以采用多種算法自動進行。本文通過模擬LAMOST光譜的方式,對目前擬采用的交叉相關(guān)算法在各種條件下的運算精度進行分析,研究了各因素對視向速度精度測量的影響。通過本文工作,可以對將來發(fā)布數(shù)據(jù)的測量結(jié)果進行評價,給出置信區(qū)間和精度,為LAMOST的科學(xué)產(chǎn)出提供可靠的數(shù)據(jù)處理的保證。 本文的主要工作有以下幾個方面： (1)對于不同溫度下不同類型的恒星光譜,通過理論光譜的模擬和統(tǒng)計分析,檢驗了計算視向速度時,交叉相關(guān)算法本身以及由于儀器的最小分辨率和數(shù)據(jù)采樣率等多種因素帶來的誤差。結(jié)果證實了選擇交叉相關(guān)是比較可靠且精度較高的算法。 (2)光譜在波長定標(biāo)過程中帶來誤差的原因是復(fù)雜的,有儀器的非線性原因、擬合燈譜發(fā)射線位置的誤差、擬合色散曲線帶來的誤差等等。這些因素綜合起來,在LAMOST的實際光譜定標(biāo)時,會產(chǎn)生7km/s左右的零點誤差和15km/s左右的隨機誤差,本文對此進行了模擬分析。 (3) LAMOST儀器的效率是隨波長變化的,觀測得到的光譜往往疊加了其固有的效率曲線。對于LAMOST效率曲線在計算視向速度時的影響,在本文工作中也進行了仿真,并給出了分析結(jié)論。 (4)算法對噪聲的敏感程度,決定了視向速度的可靠性。我們將光譜疊加了按照LAMOST噪聲模型產(chǎn)生的隨機噪聲,構(gòu)造出與LAMOST實際觀測得到的光譜相似的光譜。經(jīng)過大數(shù)據(jù)量的模擬,統(tǒng)計出信噪比降低與視向速度誤差增大的關(guān)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.
【學(xué)位授予單位】：北京化工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2011
【分類號】：P141.5

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