Specifying Parameters

The recorded SED of a galaxy is a function of many parameters: some associated with the universe (i.e., object’s redshift and adopted cosmology), some dependent on a galaxy’s stars (i.e., stellar masses, ages, metallicities, initial mass functions, etc.), and some arising from the galaxy’s interstellar medium (i.e., attenuation from dust and emission from ionized gas, PAH molecules, and dust). For any individual calculation, some of these parameters will be fixed and some will be allowed to vary. For the “free” parameters, it is usually necessary to provide some constraints on their values, either to ensure that the final result are physical, or to limit the degrees of freedom in a calculation.

The easiest way to specify parameters to MCSED is through its configuration files. The file config.py contains the top-level information about most of the important parameters that users will want access to. Alternatively, several of the most frequently used parameters can be modified via command-line arguments. If one wants to change some of MCSED’s preset options, such as the cosmology or the range of values that a parameter is allowed to take on, this can be done in individual modules, such as sfr.py and dust_abs.py. A list of the variables that a user might want to modify appears in Summary of Important Variables.