Spectroscopic and Photometric Training Data¶
SALTShaker input files use SNANA format, which allows easy synergy between model training and SN simulations, light-curve fitting, and systematic uncertainty estimation. The SNANA-formatted data necessary for training includes photometry, spectroscopy, and filter functions/photometric system information.
For photometry and spectroscopy, a number of light curves and spectra are provided
in the examples/SALT3TRAIN_K21_PUBLIC/
directory
for training. Light curves and spectra are
combined into a single file. The training data themselves are described
in Kenworthy et al., 2021.
For the photometric information, so-called “kcor” files - which confusingly contain no k-corrections - are given in the
examples/SALT3TRAIN_K21_PUBLIC/kcor
directory. These FITS-formatted files define
the photometric system associated with each survey that comprises the training sample.
The SNANA function kcor.exe
will create these files from the .input
files in the
same directory if anything needs to be adjusted. “kcor” files contain filter transmission
functions, AB, BD17, or Vega spectra depending on the photometric system of the data, zeropoint offsets,
and optional shifts to the central wavelength of each filter.
Photometry and Spectroscopy Format¶
SNANA file format consists of a number of header keys giving information about each SN, followed by photometry and spectroscopy.
An example of the minimum required header is below:
SURVEY: FOUNDATION
SNID: ASASSN-15bc
RA: 61.5609874
DEC: -8.8856098
MWEBV: 0.037 # Schlafly & Finkbeiner MW E(B-V)
Below the header, the photometry is included in the following format:
NOBS: 64
NVAR: 7
VARLIST: MJD FLT FIELD FLUXCAL FLUXCALERR MAG MAGERR
OBS: 57422.54 g VOID 21576.285 214.793 16.665 0.011
OBS: 57428.47 g VOID 30454.989 229.733 16.291 0.008
OBS: 57436.55 g VOID 26053.054 253.839 16.460 0.011
OBS: 57449.46 g VOID 11357.888 158.107 17.362 0.015
...
END_PHOTOMETRY:
The SALT3 training code only reads the MJD, FLT (filter), FLUXCAL, and FLUXCALERR values. FLUXCAL and FLUXCALERR use a zeropoint of 27.5 mag.
The beginning of the spectroscopy section is identified by the following header lines:
NVAR_SPEC: 3
VARNAMES_SPEC: LAMAVG FLAM FLAMERR
Where the columns are wavelength (angstrom), flux (erg/cm^2/s/A), and flux uncertainty (not currently used). Each spectrum has the following format:
SPECTRUM_ID: 1
SPECTRUM_MJD: 54998.378 # Tobs = -13.832
SPECTRUM_TEXPOSE: 100000.000 # seconds
SPECTRUM_NLAM: 352 (of 352) # Number of valid wavelength bins
SPEC: 4200.00 4209.35 -2.068e-10 5.701e-10
SPEC: 4209.35 4218.76 -2.704e-10 6.359e-10 2.557e-10 23.25
SPEC: 4218.76 4228.23 -2.725e-10 6.312e-10 2.543e-10 23.26
SPEC: 4228.23 4237.76 -4.588e-11 6.232e-10 2.538e-10 23.25
SPEC: 4237.76 4247.35 -8.320e-10 6.152e-10 2.541e-10 23.25
...
END_SPECTRUM: