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4 Model Formats

Yafit can understand model data in a number of formats as written by various spectral simulation codes. This list will probably need to be expanded in the future. You can contact the author if a format that you need is not here, but note that some well-defined description of a format must be available in order for a handler to be written.

YModel is the name given to the 'native' format used by Yafit for model data. It is in fact a FITS or VOTable table in which each row represents one model spectrum. The first column contains a vector of X values, and the second a vector (of the same size) of Y values, and these two therefore together define a function Y(X) which represents the spectrum. There may be any number of additional columns present, giving other information about each model. It is possible to write YModel files directly and to manipulate them using TOPCAT or STILTS, but in most cases YModel files will be written using the copymodel task.
Spectra extracted into files by Galaxev's galaxevpl (a.k.a. gpl) tool can be used. These look something like this:
    # Output file name = bc2003_hr_m42_salp_ssp_exp200.a1
    # Input file name  = bc2003_hr_m42_salp_ssp_exp200.ised
    # Column           2          3          4
    # Record          106        107        108
    # Age (yr)      4.500E+07  4.750E+07  5.000E+07
    # Lambda(A)       Flux       Flux       Flux
      9.100000E+01  6.685E-19  6.602E-19  6.520E-19
      9.400000E+01  7.586E-19  7.491E-19  7.398E-19
Output files written by the Starburst99 program can be used. These look something like this:
    MODEL DESIGNATION: eyles01100FM2       
    MODEL GENERATED ON 20060527  AT 035003.6


    .10000E+05          91.00      25.60479    25.60479   -15.00000
    .10000E+05          94.00      26.34040    26.34040   -15.00000
The Spanish Virtual Observatory (SVO) provides a service from the web page which returns grids of model spectra given certain criteria entered in an HTML form. The result it returns is a tar archive containing a number of VOTable files each of which holds a single calculated spectrum. These tar files (compressed or uncompressed) can be understood directly by Yafit as a list of model spectra.
This is an ad-hoc format which can be used to store model data in a standard tabular format as a VOTable. The first column of the table is used to store X (wavelength) values, and each subsequent column stores the Y (flux) values for a different model spectrum. All the Y values in the Nth row correspond to the X value in that row and so on. An M-column sideways table contains M-1 model spectra. The only additional information about each spectrum is a name or label, which is supplied by the column name of the column which it represents.

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