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FORS2 Pipeline:
Recipe for Spectroscopic Calibration Data

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  • recipe name: FORS_CALIB
  • input frames: SCREEN_FLAT_LSS+LAMP_LSS, SCREEN_FLAT_MOS+LAMP_MOS, SCREEN_FLAT_MXU+LAMP_MXU
  • associated templates: FORS2_lss_cal_daycalib, FORS2_mos_cal_daycalib, FORS2_mxu_cal_daycalib
purpose: Creates all necessary calibration products to process SCIENCE data

description: This recipe identifies reference lines on LSS and MOS/MXU arc lamp exposures, and traces the spectral edges on the associated flat field exposures. With this information the spectral extraction mask to be applied in the scientific data reduction is determined. From the input flat field exposures a normalised flat field frame is also derived. The input arc lamp and flat field exposures are assumed to be obtained quasi-simultaneously, so that they would be described by exactly the same optical distortions.

products (for naming rules see here):

  • normalized master flat field (MNFL/MNFM/MNFX), derived by dividing the master screen flat by its smoothed version
  • master screen flat field (for verification only, MSFL/MSFM/MSFX), master screen flat. Comparing it to the normalized master flat allows to see if all slitlets for MOS/MXU have been found.
  • dispersion coefficients table (PWCL/PWCM/PWCX) containing the wavelength calibration polynomial coefficients. This table contains as many rows as in the reduced lamp image, ordered in the same way.
  • slit location table (PSLL/PSLM/PSLX) containing the slit positions on the CCD, and on the reduced lamp image
  • wavelength map image (PWML/PWMM/PWMX) with the same size as the CCD, where to each pixel is assigned the value of the wavelength at its center
  • spatial map image (MOS/MXU only, PSMM/PSMX), which has the same size of the CCD, where to each pixel is assigned the value of its distance (in CCD pixels) from the top edge of the spectrum it belongs to. In case of confusion between nearby spectra, the spatial coordinate would just reflect the spectral curvature, and not the absolute spatial coordinate along the slit (see manual for more details).
  • spectral resolution table (PSRL/PSRM/PSRX) containing the mean spectral resolution for each reference arc lamp line
  • curvature coefficients table (MOS/MXU only, PCCM/PCCX) containing the coefficients of the polynomials used to fit the spectral curvature
  • reduced lamp image (for verification only, PRLL/PRLM/PRLX), i.e. rectified and wavelength calibrated arc lamp image. This is the result of applying the extraction mask derived from the flat field and arc lamp exposures to the input arc lamp exposure itself. This image is just useful to get an immediate feeling of the goodness of the computed extraction mask.
  • global distortion table containing the modeling of the coefficients of the local distortion models listed in the dispersion coefficients table and the curvature coefficients table. This table is currently used just for quality control, and is produced only if at least 12 spectra are found on the CCD.

Master PS GIF Header
F2_MNFL_061029A_G300V_GG375_S13_C1hi_2x2s
F2_MNFL_061029A_G300V_GG375_S13_C2hi_2x2s
F2_PRLL_061029A_G300V_GG375_S13_C1hi_2x2s
F2_PRLL_061029A_G300V_GG375_S13_C2hi_2x2s
F2_PWML_061029A_G300V_GG375_S13_C1hi_2x2s
F2_PWML_061029A_G300V_GG375_S13_C2hi_2x2s
F2_MNFX_061023A_G600RI_GG435_Sp930446_C1hi_2x2s
F2_MNFX_061023A_G600RI_GG435_Sp930446_C2hi_2x2s
F2_PRLX_061023A_G600RI_GG435_Sp930446_C1hi_2x2s*
F2_PRLX_061023A_G600RI_GG435_Sp930446_C2hi_2x2s
F2_PSMX_061023A_G600RI_GG435_Sp930446_C1hi_2x2s
F2_PSMX_061023A_G600RI_GG435_Sp930446_C2hi_2x2s
F2_PWMX_061023A_G600RI_GG435_Sp930446_C1hi_2x2s
F2_PWMX_061023A_G600RI_GG435_Sp930446_C2hi_2x2s


*The S-shaped lines come from slanted slitlets. Those are not handled well with the default parameters, but can be handled with manually adjusted parameters.

 


 
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