data products of guoshoujing telescope(lamost) pipeline and current problems luo ali@kiaa lamost...
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![Page 1: Data products of GuoShouJing telescope(LAMOST) pipeline and current problems LUO Ali@KIAA LAMOST Workshop](https://reader035.vdocuments.us/reader035/viewer/2022062217/56649f1b5503460f94c3080f/html5/thumbnails/1.jpg)
Data products of GuoShouJing telescope(LAMOST) pipeline and c
urrent problems
LUO Ali@KIAA
LAMOST Workshop
![Page 2: Data products of GuoShouJing telescope(LAMOST) pipeline and current problems LUO Ali@KIAA LAMOST Workshop](https://reader035.vdocuments.us/reader035/viewer/2022062217/56649f1b5503460f94c3080f/html5/thumbnails/2.jpg)
Outline
• Data products
• Progress and problems of 2d pipeline
• Progress of 1d pipeline
• Commissioning data request.
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Formal Data products
• Calibrated 1d spectra
• Catalog
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Progress and problems of 2d pipeline
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Fiber profile
• Fit fiber profile by flat exposure
• Use this profile within other exposures
• That is:
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Flux extraction
• Profile fitting– Good at working against bad pixels, crosstalk,
etc.– Bad at extracting emission lines
• The function varies at center and edge of profile
• Aperture– Fast extracting– For LAMOST, adjacent fibers are far enough
from each other
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Flat extraction
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Object extraction
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Wavelength calibration
• First, calibrate with arc lamp lines
• Then corrected by sky emission lines
• Problem:– Low S/N at 3600Å– Weak arc lamp lines after 7500Å– Image shifts from arc exposure to object
exposure, so the error could increase to 0.2Å from 0.1Å
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Stability of spectrograph
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Fiber flat
• Fitting a ‘super-flat’ by all fibers
• Divide ‘super-flat’ to get fiber flat
• Problem:– Flat is not flat enough to correct fiber
throughput– Need to improve field flat
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Lamp flat vs. night sky
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Night sky vs. twilight flat
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Sky subtraction
• n sky fibers, fitting a ‘super-sky’
• Need:– Good extraction– Accurate wavelength calibration– Good flat– Good sky emission line profiles
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Flux calibration
• By SDSS standard stars
• Correct observed flux by template
• Telluric correction
• Problem:– Some standard stars get no information– Low S/N
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Spectrum combination
• Different exposures
• Blue and red part
• Problem:– Too low S/N at the beginning and end of each
spectrum
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Examples
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Progress of 1d pipeline• Classification and redshift (rv) measurement depends on
quality of data• Stellar parameters
compare of SSPP and ULySS (interpolate in Elodie)
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New version of Elodie-Prugniel et al 2010 in preparation
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Validation of ULySS with CFLIB
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Comparison of SSPP with high resolution spectra
(Allende Prieto et 2008)
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Comparison of ULySS with high resolution spectra
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Validation of ULySS with SSPP calibrated result
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SSPP(v7.5) & ULySS(v)
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Problem: template and calibration
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Commissioning data requestLAMOST Commissioning data Application( Only available during LAMOST commissioning)
Applicant Name(Sign): Date:
Institution:
Email:
Data class (objects, observation date, data amount, original data, 1d spectra, parameters):
Purpose (should announce the data will not be used for other purpose):
Feedback (content and time, science production):
LAMOST opinion
Sign: date: