1 / 12

LAMOST 2D Pipeline

This document outlines the file naming and storage conventions for the LAMOST 2D pipeline, including data class, type, color, plan ID, run, and modified Julian Day.

celestev
Download Presentation

LAMOST 2D Pipeline

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. LAMOST 2D Pipeline Jianjun Chen, Zhongrui Bai, Hanqin Qin Xulei Xue NAOC CAS, USTC 2008-12-3, Beijing

  2. 2D file name and storage Example: rs-16b-7654321-03 –77174720.fit Class+type-spID+color-planID-run-MJD • Data class: r(raw), p(product),t (temporary) • Data type: o(object), s(sky), f(flat), b(bias),a(arc), t(test) • spID: 1-16 for low-res spectrographs 17-32 for mid-res spectrographs

  3. 2D file name and storage • Color: r(red), b(blue) • planID: plan ID from SSS • Run: the run number during each night • MJD: modified Julian Day, but here modified to in unit of minute • Data from each night stored in directory named by MJD or calendar date

  4. 2D pipeline • Scan files and pre-reduction • Tracing and extraction • Wavelength calibration • Flat correction • Sky subtraction • Flux calibration, combine 3 exposures and red & blue spectra

  5. Scan files and pre-reduction • Subtract bias • Calculate inverse variance as noise • Scan files and read files to corresponding structures

  6. Tracing and extraction • Find out the center positions of fiber profiles at ystart in a flat exposure • Along the dispersion direction, find the center and width for each fiber profile • Fit the fiber profiles along spatial direction to calculate the flux for each fiber rs-12r-20081011-skyimage.fits ro-12r-20081012-47-78799941.fit ro-16-20081001-376-78784084.ps

  7. Wavelength calibration • Iteratively calculate the correlation coefficient of one fiber arc lines with lines in table, to get the initial wavelength solution • Based on the line table, separate the arc spectrum next to the initial arc to sections, in each section only one strong line, and calculate the dispersion curve • Go to next arc spectrum, do it again 1D-rs-12r-20081011-15-78799307'.ps

  8. Flat correction • Using B-spline to fit wave and flux in good fiber and to reconstruct the superflat • Divide the flat flux by superflat and get fiber efficiency curve fflat • Object flux divide fflat

  9. sky subtraction • Locate sky emission lines, to correct the wavelength calibration • Calculate the emission line width • Using B-splines to reconstruct supersky • Subtract the supersky from object flux

  10. Flux calibration (SDSS sky area) • Compare standard star flux (F-type sub dwarf) with flux of standard model, to derive spectrophotometric calibration • Combine 3 exposures • Combine red and blue

  11. Some tests • 20081003sky_eff\FiberEff-12-r-flux.fit.ps • 1D-ro-15r-20081001-376-78784084.fit.ps • skysub-1D-ro-15r-20081001-376-78784084.fit.ps

  12. Thanks!

More Related