本文選題：CFHTLS + PSF　； 參考：《上海師范大學(xué)》2013年碩士論文

【摘要】：理論和觀測結(jié)果對(duì)比表明：宇宙中絕大部分物質(zhì)是不發(fā)光的，且這些物質(zhì)無法使用光學(xué)觀測方法觀測。通過對(duì)引力透鏡的研究可以得到透鏡天體的引力場的物質(zhì)分布情況。當(dāng)前弱引力透鏡研究的主流方法是宇宙剪切  由宇宙大尺度結(jié)構(gòu)所引起的弱引力透鏡現(xiàn)象，其精度主要取決于對(duì)星系形狀的精確測量。點(diǎn)擴(kuò)散函數(shù)（Point Spread Function，簡稱PSF）是一個(gè)描述點(diǎn)源（例如恒星）變成面源的函數(shù)，是天體物理研究必須考慮的問題。遙遠(yuǎn)天體發(fā)出的光在到達(dá)望遠(yuǎn)鏡終端CCD的過程中，會(huì)受到大氣抖動(dòng)、大氣湍流、大氣視寧度（seeing）和望遠(yuǎn)鏡自身扭曲等因素的影響，最終使得該遙遠(yuǎn)天體在CCD上的成像發(fā)生扭曲形變。通過尋找一個(gè)合適的PSF能夠修正這些干擾因素對(duì)成像的影響，從而能夠精確測量星系的橢率，進(jìn)而提高宇宙剪切對(duì)宇宙學(xué)參數(shù)限定的精度。本文研究的數(shù)據(jù)源自加拿大天文數(shù)據(jù)中心（CADC）的CFHTLS（Canada-France-Hawaii Telescope LegacySurvey）深度巡天第六次釋放r′波段的D1、D2、D3和D4這4個(gè)天區(qū)最好視寧度25%的數(shù)據(jù)。本文以CFHTLS Deep巡天第二天區(qū)為例展開論述（簡稱D2-r′-25）。通過對(duì)點(diǎn)擴(kuò)散函數(shù)的修正改進(jìn)來提高CFHTLS望遠(yuǎn)鏡深度巡天星系成像橢率的測量精度。本文通過兩種方法來提高點(diǎn)擴(kuò)散函數(shù)(PSF)的修正改進(jìn)：第一種PSF修正的方法是整體擬合，即以一個(gè)平方度天區(qū)的圖片為單位進(jìn)行整體的擬合，先對(duì)高質(zhì)量恒星樣本做PSF修正，然后將恒星的PSF擬合修正推廣到星系的PSF擬合修正。第二種方法將一個(gè)平方度天區(qū)的圖片按PSF圖形情況手動(dòng)分割成若干塊（本文分割成4塊），然后對(duì)每一小塊天區(qū)采用低階擬合。兩種PSF擬合修正的區(qū)別在于：對(duì)整體擬合而言，可能某些地方出現(xiàn)過度擬合，，某些地方出現(xiàn)擬合不夠；對(duì)分割后每個(gè)子天區(qū)采用低階擬合而言，能夠更好的控制擬合函數(shù)的選取和擬合程度的控制等具體情況。通過比較這兩種擬合結(jié)果，來確定CFHTLS Deep的PSF修正方式，并計(jì)算星系的剪切兩點(diǎn)相關(guān)函數(shù)。
[Abstract]:The comparison of theoretical and observational results shows that the vast majority of matter in the universe is not luminous, and these materials cannot be observed by optical observation method. Through the study of gravitational lensing, the mass distribution of gravitational field of lens celestial body can be obtained. At present, the main method in the study of weak gravitational lensing is the phenomenon of weak gravitational lensing caused by the cosmic large scale structure. Its accuracy mainly depends on the accurate measurement of the shape of galaxies. Point Spread function (PSF) is a function that describes the point source (such as a star) becoming a point source, which must be considered in the study of astrophysics. The light emitted by distant celestial bodies is affected by atmospheric jitter, atmospheric turbulence, atmospheric visibility and distortion of the telescope itself as it reaches the telescope terminal CCD. Finally, the image of the distant object on the CCD is distorted and deformed. By looking for a suitable PSF, the influence of these interference factors on imaging can be corrected, thus the ellipticity of galaxies can be accurately measured, and the precision of cosmic shear defining cosmological parameters can be improved. The data in this paper are derived from the CFHTLS(Canada-France-Hawaii Telescope Legacy Survey of the Canadian Astronomical data Center (CADC) for the sixth time to release the data of D1D2D3 and D4 in the R 'band with the best visibility of 25%. This paper takes the second day area of CFHTLS Deep survey as an example. By modifying the point diffusion function, the measurement accuracy of the ellipsometry of the CFHTLS telescope's depth survey galaxy imaging is improved. In this paper, the point diffusion function (PSF) is improved by two methods: the first method of PSF correction is global fitting, that is, the whole fitting is based on a square sky image, and the high mass star sample is first modified by PSF. Then the PSF fitting correction of stars is extended to the PSF fitting correction of galaxies. In the second method, a square area image is manually divided into several blocks according to the PSF graph (this paper divides into 4 blocks, and then uses low-order fitting for each small area of sky. The difference between the two PSF fitting amendments lies in the fact that, for the whole fitting, there may be over-fitting in some places and insufficient fitting in some places; for each sub-area after segmentation, low-order fitting is used. It can better control the selection of fitting function and the control of fitting degree. By comparing these two fitting results, the PSF correction method of CFHTLS Deep is determined, and the two-point correlation function of galaxy shear is calculated.
【學(xué)位授予單位】：上海師范大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2013
【分類號(hào)】：P14

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本文編號(hào)：1787134