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 \(x_{\text{HeII}} = x_{\text{HII}}\), and set \(x_{\text{HeIII}} = 0\)
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 \(\sigma \propto \nu^{-3}\)

Default: 0

approx_lwb

0. Solves RTE (i.e., full “sawtooth” background).

1. Assume flat spectrum between Lyman-\(\alpha\) 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 \(S_{\alpha} = 1\)

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-\(\alpha\) 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