GMOS Data Reduction

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Flatfield Correction• GCALflats for Nod & Shuffle programs are not shuffled when theyare taken ⇒ use fl_double+ option in gsflat.• When constructing Nod & Shuffle GCALflats with fl_double+, mustspecify the shuffle distance in the parameter nshuffle to match thevalue given in the NODPIX keyword in the science data.• Flats are useful for removal of pixel-to-pixel variations in brightertargets• Flats are important for removal of fringing in bright objects• gnscombine applies flatfield before sky subtraction ⇒ flat cannotbe gmosaic’d ⇒ use fl_detec+ option in gsflat– N.B. in general it is good practice to use fl_detec+ when workingwith long wavelength data because any function of high enoughorder to fit the full spectral range for most gratings will also startto fit the fringing.
gsflat (N&S)gsflat @flatfiles_460 out=Flat_460.fitslogfile=gmos.logfile rawpath="rawdata$”fl_over+ fl_trim+ nbiascontam=4fl_bias+ bias=“sciencebias” fl_darkfl_fixpix-fl_inter+ function=“chebyshev”order=15 fl_detec+ fl_double+nshuffle=1536 ovs_flinter+ fl_vardq+fl_detec+: do not mosaic, fit each detector independentlyovs_flinter+: examine fits to overscan region interactivelyfl_double+: create double flat shifted by same amount as sciencedatanshuffle=1536: shuffle distance (unbinned pixels) from NODPIXheader keyword in science data
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Reducing GMOSSpectroscopic dataRica
Page 3 and 4:
General Principles• Record everyt
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Notes on Bias and Dark• Standard
Page 8 and 9: Overscan “Spillover”R400 gratin
Page 10: Reduced combined 2x1 biasimage, con
Page 13 and 14: Difference image of two reduced sta
Page 15 and 16: Flatfield Correction• Flats may b
Page 17 and 18: gsflatgsflat @flatfiles_460 out=Fla
Page 19 and 20: gsflatFitting the overscan region:
Page 21 and 22: gsflatFitting the “response” fu
Page 23 and 24: gsflatλRed flat field along the sp
Page 25 and 26: gsflatThere is a trade off between,
Page 27 and 28: Alignment starsGMOS MOS Spectra
Page 29 and 30: GMOS MOS reductionThe yoffset param
Page 31 and 32: gswavelengthgswavelenth @gsNarcfile
Page 33 and 34: gswavelengthDetermine wavelength so
Page 35 and 36: gswavelengthAutomatic line identifi
Page 37 and 38: gswavelengthFinding the wavelength
Page 39 and 40: gswavelengthOutput after fitting wa
Page 41 and 42: gswavelengthFinding the 2D waveleng
Page 43 and 44: gstransformgstransform gsNarcfile.f
Page 45 and 46: gsextractgsextract @tgsNsciencefile
Page 48 and 49: Raw Longslit N&SSpectrum
Page 50 and 51: Observing Tool N&SComponent2010B
Page 52 and 53: N&S Dark Correction• N&S darks ta
Page 54 and 55: Overscan fit for CCD1. By utilizing
Page 56 and 57: Zoom of reduced spectral image wher
Page 60 and 61: Final normalized spectral image. Mi
Page 62 and 63: N&S Sky Subtraction• Sky subtract
Page 64 and 65: Bias corrected, dark subtracted, fl
Page 66: Bias Correction• Not talking abou
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GMOS Data Reduction

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