Data Flow and Automatic photometry Pipeline课件.ppt

Data Flow and Automatic photometry Pipeline 陳炳志 章展誥 成功大學物理系 精品文档 Data Flow Calibration Bias Dark Flat Field Automatic photometry pipeline Object matching and light curve generation — IRAF — IRAF — IDL XMgr 精品文档 Automatic photometry pipeline 架構在IRAF/DAOphot package上 (Stetson, 1987, PASP) 減少Coding的時間 減少犯錯的機會 參數越少越好 減少人為判斷的錯誤或差異 精品文档 DAOPhot (Crowd field photometry) Daofind Locate stellar-like objects in the field Key parameters：std. deviation of background, FWHM, detection threshold, data maximum Phot Aperture photometry Derive the magnitude as an initial value of PSF fitting Key parameters：aperture radius, inner sky radius , annulus width of the sky, centering box size 精品文档 DAOPhot (Crowd field photometry) Pstselect Select candidate PSF stars Key parameters: psf radius Criteria: recruit by the order of magnitude and no other stars or image edges falling into psf radius Psf Construct analytic form of PSF Key parameters: psf radius, fit radius, match radius, psf form 6 analytic function form: gaussian, lorentz, moffat15, moffat25, penny1, penny2 精品文档 DAOPhot (Crowd field photometry) Manual operation → Select/reject candidate stars recruited by pstselect Bad candidate stars often selected by pstselect Faint objects which is not detected by daofind falling into fwhm radius Saturated stars or nearby objects Objects which is not saturated but become non-linear in the core region Allstar Solve the stellar photometry by psf fitting Check the data quality by the subtracted image 精品文档 DAOPhot (Crowd field photometry) Parameters 可以分為幾類： 與望遠鏡/CCD相關的參數：data maximum 和觀測環境有關參數：FWHM, sky deviation 可以由上面參數導出的參數：centering box size, aperture radius, inner sky radius…… KEY PARAMETER→FWHM, sky deviation Sky deviation 可以藉由 recursive 3-σ rejection的方式得到→僅剩下FWHM需要量測輸入 精品文档 Parameters Data maximum = 50000 Detection threadhold = 3.5 S=0.4246 * fwhm Centering box size = 2.0*fwhm Max shift = 2.0 Aperture radius = 5*S Inner sky radius = 6*S Annulus width of the sky: minimum 2 and consist