Emission-line Moments

Analysis class: EmissionLineMoments

Method definition: EmissionLineMomentsDef


Reference file:

  • Before Gaussian emission-line modeling:


  • After Gaussian emission-line modeling:


Config files: $MANGADAP_DIR/mangadap/config/emission_line_moments

Example config: emomm.ini

key                = EMOMMPL9
minimum_snr        = 0.0
artifact_mask      = BADSKY
emission_passbands = ELBMPL9
redo_postmodeling  = True
fit_vel_name       = Ha-6564

Important class dependencies:

  • mangadap.proc.bandpassfilter: Provides the core functions that perform the bandpass integrals.

  • EmissionMomentsDB: Generalized class that provides the detailed parameters for a set of emission-line windows used to perform non-parametric moments.

  • EmissionLineFit: Provides functions common to both the moment and Gaussian-fit calculations.

  • SpectralPixelMask: Used to mask spectral regions.


  • Read the artifact database to setup the SpectralPixelMask object based on the artifact_mask config.

  • Set up the EmissionMomentsDB using the emission_passbands config.

  • Determine the binned spectra above the S/N limit set by the minimum_snr config.

  • Use the StellarContinuumModel object to construct the stellar continuum for each binned spectrum.

  • Subtract the continuum using 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 measure_moments().

    • Redshift the emission-line passbands based on the provided redshift.

    • Determine the pseudo-continuum in the red and blue bands using 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 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 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 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.