salt2
================================================

SALT2 supernova distance modulus likelihood

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| File        | supernovae/salt2/salt2_interface.py                                    |
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| Attribution | CosmoSIS Team                                                          |
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|             | K. Barbary                                                             |
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| URL         |                                                                        |
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| Citations   | https://www.aanda.org/articles/aa/abs/2007/16/aa6930-06/aa6930-06.html |
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This module implements a likelihood for Type Ia supernova distance
measurements using SALT2 light curve fits. SALT2 is a spectral template
method for standardizing supernova luminosities.

The module reads SALT2 fit results including apparent magnitude (mB),
color (c), and stretch (x1) parameters along with their covariances,
and computes the likelihood comparing predicted distance moduli to
the SALT2-derived values.


Assumptions
-----------

 - SALT2 light curve fitting has been performed
 - Supernova data includes distance modulus and light curve parameters



Setup Parameters
----------------

.. list-table::
   :header-rows: 1

   * - Name
     - Type
     - Default
     - Description

   * - dirname
     - str
     - module directory
     - Directory containing SALT2 data files
   * - filename
     - str
     - SALT2.FITRES
     - Name of SALT2 fit results file


Input values
----------------

.. list-table::
   :header-rows: 1

   * - Section
     - Name
     - Type
     - Default
     - Description

   * - supernova_params
     - alpha
     - real
     - 
     - SALT2 stretch-luminosity parameter
   * - 
     - beta
     - real
     - 
     - SALT2 color-luminosity parameter
   * - 
     - M
     - real
     - 
     - Absolute B-band magnitude
   * - 
     - DeltaM
     - real
     - 
     - Host galaxy mass correction (if used)
   * - distances
     - z
     - real 1d
     - 
     - Redshift values for distance calculations
   * - 
     - d_l
     - real 1d
     - 
     - Luminosity distance in Mpc


Output values
----------------


.. list-table:: Output values
   :header-rows: 1

   * - Section
     - Name
     - Type
     - Description

   * - likelihoods
     - salt2_like
     - real
     - Log-likelihood from SALT2 supernova data