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emissionmom.rst

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Emission-line Moments

Analysis class: ~mangadap.proc.emissionlinemoments.EmissionLineMoments

Reference root: see ~mangadap.config.analysisplan.AnalysisPlan.method_path; $MANGA_SPECTRO_ANALYSIS/$MANGADRP_VER/$MANGADAP_VER/[METHOD]/[PLATE]/[IFUDESIGN]/ref for MaNGA

Reference file: see ~mangadap.proc.emissionlinemoments.EmissionLineMoments.default_paths; for MaNGA the files are:

  • Before Gaussian emission-line modeling:

    • manga-[PLATE]-[IFUDESIGN]-[RDXQA]-[BINNING]-[CONTINUUM]-[ELMOM].fits.gz

  • After Gaussian emission-line modeling:

    • manga-[PLATE]-[IFUDESIGN]-[RDXQA]-[BINNING]-[CONTINUUM]-[ELFIT]-[ELMOM].fits.gz

Optional Parameters: see plan. The table below lists the parameters defined by ~mangadap.proc.emissionlinemoments.EmissionLineMomentsDef

Important class dependencies:

  • mangadap.proc.bandpassfilter: Provides the core functions that perform the bandpass integrals.
  • ~mangadap.par.emissionmomentsdb.EmissionMomentsDB: Generalized class that provides the detailed parameters for a set of emission-line windows used to perform non-parametric moments.
  • ~mangadap.proc.spectralfitting.EmissionLineFit: Provides functions common to both the moment and Gaussian-fit calculations.
  • ~mangadap.util.pixelmask.SpectralPixelMask: Used to mask spectral regions.

Algorithm:

  • Read the artifact database to setup the ~mangadap.util.pixelmask.SpectralPixelMask object based on the artifact_mask config.
  • Set up the ~mangadap.par.emissionmomentsdb.EmissionMomentsDB using the emission_passbands config.
  • Determine the binned spectra above the S/N limit set by the minimum_snr config.
  • Use the ~mangadap.proc.stellarcontinuummodel.StellarContinuumModel object to construct the stellar continuum for each binned spectrum.
  • Subtract the continuum using ~mangadap.proc.spectralfitting.EmissionLineFit.subtract_continuum. WARNING: If a binned spectrum does not have a fitted stellar continuum, the moment analysis is performed on the binned spectrum without any continuum subtraction.

  • Measure the moments using ~mangadap.proc.emissionlinemoments.EmissionLineMoments.measure_moments.

    • Redshift the emission-line passbands based on the provided redshift.
    • Determine the pseudo-continuum in the red and blue bands using ~mangadap.proc.bandpassfilter.pseudocontinuum.
    • Set the slope and intercept of a linear continuum extrapolation between the two sidebands for all emission-lines.
    • For each emission line, measure the first 3 moments of the pseudo-continuum-subtracted spectra using ~mangadap.proc.emissionlinemoments.EmissionLineMoments.single_band_moments:

      (0) integrated flux; (1) intensity weighted redshift (cz); and (2) intensity weighted (cz)2.

    • Determine the instrumental dispersion at the 1st moment locations of each line using ~mangadap.proc.spectralfitting.EmissionLineFit.instrumental_dispersion.
    • Flag any measurement without a continuum spectrum as NOCORRECTION.
    • If any of the passbands (blue, red, main) are incomplete (or empty) due to masked pixels or straddle the jump between where there is and is not a viable continuum subtracted, or if that jump occurs between the blue and red passbands, flag the moments as FITFAILED in the MAPS file.
    • Mask any "dummy" bands. Dummy bands are used to ensure that the emission-line moment channels match the emission-line Gaussian-fit channels in the output MAPS file.
  • Using the 0th moment (integrated flux) and the binned spectra (''without'' continuum subtraction), measure the emission-line equivalent widths using ~mangadap.proc.bandpassfilter.emission_line_equivalent_width.
  • Construct emission-line-moments BINID map. Bin IDs are the same as for the binned spectra except that any bin that does not meet the S/N limit are given a emission-line-moment bin ID of -1.