Line strengths
Purpose
The lineStrengths
module measures line strength indices from the observed spectra. nGIST is currently equipped with one routine that can readily be used by setting the configuration parameter LS: METHOD
to 'default'
. In particular, this routine employs a Python translation of the line strength measurement routine of Kuntschner et al. (2006) and the routine of Martin-Navarro et al. (2018) in order to match the measured line strength indices to single stellar population equivalent population properties.
Config file input
LS :
METHOD : False #'default' # Name of the routine in lineStrengths/ (without .py) to perform the tasks. Set 'False' to turn off module. Set 'default' to use the standard GIST implementation, exploiting the routines of Kuntschner et al. (2006) and Martin-Navarro et al. (2018).
TYPE : 'SPP' # Set 'LS' to only measure line strength indices, or 'SPP' to also match these indices to stellar population properties.
LS_FILE : 'lsBands.config' # File to define the wavelength band of the line strength indices to be measured. The specified path is relative to the configDir path in defaultDir.
CONV_COR : 8.4 # Spectral resolution [in Angst.] at which the line strength indices are measured.
SPP_FILE : 'MILES_KB_LIS8.4.fits' # File providing predictions on line strength indices for a set of single stellar population models
MC_LS : 30 # Number of Monte-Carlo simulations in order to obtain errors on the line strength indices. Note: This must be turned on.
NWALKER : 10 # Number of walkers for the MCMC algorithm (used for the conversion of indices to population properties)
NCHAIN : 100 # Number of iterations in the MCMC algorithm (used for the conversion of indices to population properties)
LSF_TEMP : 'lsf_MILES' # Path of the file specifying the line-spread-function of the spectral templates. The specified path is relative to the configDir path in defaultDir.
TEMPLATE_SET : 'miles' # options are 'miles' or 'IndoUS'
LIBRARY : 'MILES/' # options are 'MILES/', 'miles_ssp_ch/', or 'IndoUS/'
NORM_TEMP : 'LIGHT' # Normalise the spectral template library to obtain light- or mass-weighted results [LIGHT / MASS]
Output
Files
All outputs are available in the OrigRes
and AdapRes
versions, as derived at the original and adapted spectral resolution of the spectra.
-
_ls.fits
, Extension 1: Line strength indices and their errors as estimated from MC-simulations-
Columns:
Fe5015
Line strength index, names as defined inlsBands.config
|ERR_*
Errors on the line strength indices as estimated from MC-simulations -
Rows: One line per bin
-
-
_ls.fits
, Extension 2: Single stellar population equivalent population properties as estimated with a MCMC algorithm from the line strength indices-
Columns:
[lineLabel]_PERCENTILES
Percentiles of the resulting MCMC distribution for the line denoted [lineLabel] inlsBands.config
-
Rows: One line per bin
-
-
_ls-cleaned_linear.fits
: Extension 1:-
Emission-subtracted, linearly binned spectra
-
Columns:
SPEC
Emission-subtracted, linearly binned spectra |ESPEC
Variance spectra -
Rows: One line per bin.
-
-
_ls-cleaned_linear.fits
: Extension 2:- Columns:
LAM
The corresponding wavelength array
- Columns:
Function returns
The module should end with return(None)
. If an uncaught exception occurs in the module, all following modules will be skipped for this galaxy. If you intend to manually skip all subsequent modules, simply raise an exception.