emissionmom.rst

Emission-line Moments

Analysis class: :class:`~mangadap.proc.emissionlinemoments.EmissionLineMoments`

Method definition: :class:`~mangadap.proc.emissionlinemoments.EmissionLineMomentsDef`

Reference root: $MANGA_SPECTRO_ANALYSIS/$MANGADRP_VER/$MANGADAP_VER/[PLATE]/[IFUDESIGN]/ref

Reference file:

• Before Gaussian emission-line modeling:

  • manga-[PLATE]-[IFUDESIGN]-[DRPQA_KEY]-[BIN_KEY]-[CONTINUUM_KEY]-[ELMOM_KEY].fits.gz

• After Gaussian emission-line modeling:

  • manga-[PLATE]-[IFUDESIGN]-[DRPQA_KEY]-[BIN_KEY]-[CONTINUUM_KEY]-[ELFIT_KEY]-[ELMOM_KEY].fits.gz

Config files: $MANGADAP_DIR/mangadap/config/emission_line_moments

Example config: emomm.ini

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

Important class dependencies:

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

Algorithm:

• Read the artifact database to setup the :class:`~mangadap.util.pixelmask.SpectralPixelMask` object based on the artifact_mask config.

• Set up the :class:`~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 :class:`~mangadap.proc.stellarcontinuummodel.StellarContinuumModel` object to construct the stellar continuum for each binned spectrum.

• Subtract the continuum using :func:`~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 :func:`~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 :func:`~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 :func:`~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 :func:`~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 :func:`~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.