Get spectra for a set of Star-Formation Histories

This tool should be use to obtain the spectra, line-strength and photometric predictions for a given set of star formation histories (SFHs). The SFHs can be user-defined or compliant with some parametric forms. It allows the adjustment of the resulting spectra to a particular instrumental setup and format. This tool is useful to be able to directly compare the models with data from the user. The output spectra are given in units of Fλ/ Lo Mo-1Å-1.

  • Pick the SSP library to use.
  • Select the IMF type and slope you desire.
    [Note that the slope has to be fixed for parametric SFHs]
  • Select the desired alpha-enhancement mode.
    [Note that it has to be basedFe, +0.0 or +0.4 for parametric SFHs]
  • Choose between Parametric or User-defined SFH definition.
  • Load the filename with the desired SFH.
  • The contents of the file should conform to the following notation:

    • Parametric SFH

      Please do NOT mix different parametric SFHs into the same file. While allowed, it can lead to undesired results

      • Truncated
        Constant SFR between the starting age and the age of truncation, zero elsewhere.
        • trunc <start age> <age of truncation> <metallicity>
          FORMAT: <char> <float> <float> <float>
      • Exponential
        Exponential-declining SFH including a power-law rising at early times in the form:
        SFR(t)=(((<start age> - t)/<start age>)n) * e(-(<start age> - t)/tau)
        • exp <start age> <tau> <n> <metallicity>
          FORMAT: <char> <float> <float> <float> <float>
      • Exponential + Bursts
        Up to 5 burst to be added to the exponential SFH. The vector <A> is the strength of the burst, in terms of fraction of total (exp + burst) mass formed at <age>. The sum of the bursts strengths - sum<A> - also gives the fraction of mass formed in the bursts. If sum<A> is greater than 1, all the stars are assumed to be formed in the bursts and the strengths are normalized such that sum<A>=1.
        • expB <age> <tau> <n> <metallicity> <Nbursts> <age1> <A1> <metallicity1> ...
          FORMAT <char> <float> <float> <float> <float> <int> 15(<float>)>
      • Multiple SSP bursts
        Up to 5 bursts are allowed with different ages and different metallicities. The sum<A> of the bursts is always normalised to 1.
        • Npop <Nbursts> <age1> <A1> <metallicity1> <imf slope1> <alpha1> <age2> ...
          FORMAT: <char> <int> (<float>)
    • User-defined SFH
      The structure is such that the ages of all possible populations are defined in the first column, the mass fraction, metallicity, imf slope and alpha follows in subsequent columns:
      • #<ages> <mass fraction 1> <metallicity1> <imf slope1> <alpha1> <mass fraction 2> <metallicity2> ...
        FORMAT: 201(<float>)
        IMPORTANT NOTE: For the user defined SFH the output SFH is computed on the age, metallicity, imf, and alpha grid of the models. The closest SSP model to the desired parameters will be used. Therefore, at present, no interpolation is performed on the SSP libraries spectra.

  • In the Output Parameters boxes
    • Enter the desired instrumental configuration in the boxes. For convenience the boxes are filled by default with the limits of the stellar parameters of the chosen library at the nominal wavelength and resolution, but edit the different values at will.
    • For the computation of photometric magnitudes from the spectra, the user should load a file with the desired filter responses as well as choosing a reference zeropoint from the options provided. If no file is uploaded, we will use a default one (filters_default.res). Please use that file as guideline for your own filter file. Magnitudes correponding to filters which are not fully contained within the requested wavelength range will be assigned a -99.99 value.
  • Press the 'Submit Query' button.

All the time values must be expressed in Gyr and are intended to be lookback times. Up to 100 SFHs can be computed in one query. Note that for the parametric SFH each line in the input file corresponds to one SFH. In the user-defined SFH different SFHs are inserted by columns. (Nsfh=0.25*(Ncolumns-1) )

EXAMPLE files:

The first line of the files should contain the desired prefix for the output files.


Npop      2    10.    0.5    0.    0.3    0.    8      0.5    0.    1.3    0.5


exp        13.6    2.0     0.0    -2.32


0.5    0.     0.2    2.3    0.05    0.0    0.0    0.0    0.0   
1.      0.     0.0    1.3    0.05    0.0    0.0    0.0    0.0
2.      0.     0.0    1.3    0.05    0.0    0.0    0.0    0.0
3.      0.     0.0    1.3    0.05    0.0    0.0    0.0    0.0
8.0    0.5    0.0    0.3    0.00    0.8    0.0    1.3    0.5
10.0  0.5     0.0   1.3    0.50    0.2    -0.4    0.3    0.0

On output, a new window will open with the progress of your query. The program will produce one outputfile for each spectrum to be computed (i.e. for each SFH inserted). The name of the files will be: <pref>+<Nsfh>+'.out'. It also produces the files with the computed SFHs normalized to 1 Msun, and Star Formation rates: <pref>+<Nsfh>+'.sfh'. An additional file with extension .mass will be created with different measurements for the mass of the output spectra. Links to the desired spectra, line-strength indices, and magnitudes will be provided. For illustration purposes, an image will appear below with the first five spectra in your query and their corresponding star-formation histories. The output files will remain in our FTP server for 10 days.

Input parameters
SSP ModelsIsochroneType of IMFIMF slope[α/Fe]SFH typeVerbose
Enter the filename with the desired SFHs (see instructions above for details)
Output parameters (help)
λInitial (Å)λFinal (Å)Δλ (Å/pix)SamplingRedshift (z)ResolutionFormat
Enter the filename with the filter responses
(Default: filters_default.res)