Stellar Kinematics
Analysis class: StellarContinuumModel
Method definition: StellarContinuumModelDef
Reference root: $MANGA_SPECTRO_ANALYSIS/$MANGADRP_VER/$MANGADAP_VER/common
Reference file: manga-[PLATE]-[IFUDESIGN]-[DRPQA_KEY]-[BIN_KEY]-[CONTINUUM_KEY].fits.gz
Config files: $MANGADAP_DIR/mangadap/config/stellar_continuum_modeling
Example config: gau_mileshc.ini
[default]
key = MILESHCMPL9
fit_type = stellar_kinematics
fit_method = ppxf
fit_iter = nonzero_templates
reject_boxcar = 100
filter_boxcar
filter_op
filter_iter
filter_degree
filter_mdegree
minimum_snr = 1.0
waverange
artifact_mask = BADSKY
emission_line_mask = ELPMPL8
template_library = MILESHC
match_resolution = False
velscale_ratio = 4
moments = 2
degree = 8
mdegree = -1
bias
Important class dependencies:
StellarKinematicsFit
: Provides the abstracted base class for stellar kinematics fits.
SpectralPixelMask
: Used to mask the fitting regions for the fit.
TemplateLibrary
: Generalized interface that provides the spectral-template library for use in spectral fitting.
PPXFFit
: Provides the core pPXF wrapper.
Algorithm:
Establish the fitting method, which includes setting up the
SpectralPixelMask
using theartifact_mask
,emission_line_mask
, andwaverange
from config.
The
BADSKY
artifact mask is read and used to build anArtifactDB
instance that masks the typical residuals around the strong sky line at 5577 angstroms.The
ELPFULL
emission-line mask is read and used to build anEmissionLineDB
instance that is used to mask the emission lines in the associated parameter file. Each mask is 1500 km/s centered on the line at the input guess redshift.The
waverange
config parameter can be used to limit the fitted spectral range; will fit as much as possible if no range is provided.Using the
SpatiallyBinnedSpectra
object, select all binned spectra with S/N greater thanminimum_snr
in config.The DAP nominally provides the stellar-continuum fit with the velocity and velocity dispersion from The DAP Datacube Configuration File as its initial guess redshift and velocity dispersion.
Instantiate the
TemplateLibrary
objects as selected by thetemplate_library
config parameter.
If matching the spectral resolution to the galaxy data (
match_resolution
in config), the resolution is matched at the redshifted wavelengths of the galaxy data, adopting the input guess velocity as the redshift.The template wavelength channel width is set to a fraction (1/
velscale_ratio
) of the galaxy data.Execute the
fit_method
selected in config. Currently, this can only beppxf
.In
fit_SpatiallyBinnedSpectra()
:
Mask binned spectra, ignoring pixels masked as
DONOTUSE
,IGNORED
,FLUXINVALID
, orFORESTAR
in DAPLOGCUBE
file.Call
fit()
with the data from theTemplateLibrary
andSpatiallyBinnedSpectra
objects.
If rejecting, the size of the boxcar (pixels) is set by
reject_boxcar
.All
filter_*
config options are only used withfit_iter=fit_reject_filter
. Do not use these options!
moments
,degree
,mdegree
, andbias
are passed directly to pPXF.Given the template and object spectral range, determine the maximum viable fitting range for pPXF using
fitting_mask()
.Run through the specified iteration procedure, as selected by
fit_iter
in config; available options are set byiteration_modes()
.Parse the pPXF results into the data table saved to the reference file.
Spectra without a fit are flagged as either
NOFIT
orFITFAILED
.Check if returned kinematics are near the imposed boundaries: \(v \pm 2000\) km/s from the input redshift and \({\rm d}v/100 < \sigma < 1000\) km/s, where \({\rm d}v\) is the size of the pixel (\(\sim 70\) km/s). Leads to The NEARBOUND flag in the
MAPS
file.Flag pixels rejected by the sigma-clipping iteration.
Calculate the dispersion corrections:
First construct three spectra: (1) the optimized template; (2) the optimized template redshifted to the best-fitting velocity and with a velocity dispersion of 100 km/s; (3) the same as spectrum 2 but also convolved to the nominal object spectrum resolution.
Use pPXF to fit spectra 2 and 3 with spectrum 1.
The quadrature difference of the fitted dispersion returned for the fit to spectrum 3 and spectrum 2 is provided as the correction (
STELLAR_SIGMACORR
in theMAPS
file)Convert the pPXF velocities and velocity errors to \(cz\) velocities in km/s using
convert_velocity()
.Construct stellar-continuum
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 stellar-continuum bin ID of -1.