:orphan:

Physics Parameters
==================

``radiative_transfer``
    0) No astrophysical sources.
    1) Includes ionization/heating from astrophysical sources.

    Default: 1

``compton_scattering``
    0) OFF
    1) Include Compton scattering between free electrons and CMB.
    
    Default: 1

``secondary_ionization``
    Determine what fraction of photo-electron energy gets deposited in various
    channels, such as heat, ionization, and excitation.
    
    0) All photo-electron energy deposited as heat.
    1) Compute using fits of Shull & vanSteenberg (1985).
    2) Compute using energy-dependent fits of Ricotti, Gnedin, & Shull (2002).
    3) Compute using look-up tables of Furlanetto & Stoever (2010).
    
    Default: 1
    
``fXh``
    Set fractional heating by photo-electrons by-hand. Currently must be a
    constant. Will override choice of ``secondary_ionization`` if supplied.
    
    Default: ``None``

``clumping_factor``
    Multiplicative enhancement to the recombination rate.
    
    Default: 1

``approx_He``
    See following table for possible behaviors depending on value of ``include_He``.
    
    Default: False
    
===============  ==============  =============== 
``include_He``   ``approx_He``    description
===============  ==============  =============== 
False                False          Neglects helium entirely
True                 True           Set :math:`x_{\text{HeII}} = x_{\text{HII}}`, and set :math:`x_{\text{HeIII}} = 0`
True                 False          Solve for helium self-consistently
===============  ==============  =============== 
    
``approx_sigma``
    0) Compute bound-free absorption cross sections via fits of Verner et al. (1996).
    1) Approximate cross-sections as :math:`\sigma \propto \nu^{-3}`
    
    Default: 0

``approx_lwb``
    0) Solves RTE (i.e., full "sawtooth" background).
    1) Assume flat spectrum between Lyman-:math:`\alpha` and the Lyman limit.
    
    Default: 1
    
``approx_xrb``
    0) Solves RTE.
    1) Heating due to instantaneous X-ray luminosity.

    Default: 1
    
``discrete_lwb``
    0) Performs integrals numerically using continuous functions for integrands (very slow)
    1) Integrates transfer equation over discrete set of points.

    Default: 1

``discrete_xrb``
    0) Performs integrals numerically using continuous functions for integrands (very slow)
    1) Integrates transfer equation over discrete set of points.

    Default: 1    
    
``approx_Salpha``
    0) Not implemented
    1) Assume :math:`S_{\alpha} = 1`
    2) Use formulae of Chuzhoy, Alvarez, & Shapiro (2005).
    3) Use formulae of Furlanetto & Pritchard (2006)
    
    Default: 1    
    
``lya_nmax``
    Default: 23
    
``lya_injected``
    Include photons injected at line-center?
    
    Default: ``True``    
    
``lya_continuum``
    Include photons redshifting into the blue-wing of the Lyman-:math:`\alpha` line?
    
    Default: ``True``
    
``recombination``
    Which recombination method to use? Can be ``"A"``, ``"B"``, or ``0``, the 
    first two options being standard case-A or case-B recombination, whereas
    the last option artificially turns off recombinations (useful for analytic
    tests).
    
    Default: ``B``