galapy.NebularFreeFree

Implements the Nebular Continuum Emission (Bremsstrahlung) component.

Functions

nff_build_params(**kwargs)

Classes

NFF(ll, **kwargs)

Class wrapping the C-core implementation of the Nebular Free-Free emission type.
class galapy.NebularFreeFree.NFF(ll, **kwargs)

Class wrapping the C-core implementation of the Nebular Free-Free emission type.

Parameters:

  • ll (float array) – the wavelength grid where the free-free emission is computed

  • **kwargs (dictionary, optional) – All possible free-parameters of the model, refer to the Keyword Arguments section.

Keyword Arguments:

  • Zgas (float) – (Optional, default = 0.01) Absolute metallicity of gas in the hosting galaxy.

  • Zi (float) – (Optional, default = 1) Average atomic number of gas in the hosting galaxy.

set_parameters(**kwargs)

Function for setting the parameters of the model.

Parameters:

**kwargs (dictionary, optional) – All possible free-parameters of the model, refer to the Keyword Arguments section.

Keyword Arguments:

  • Zgas (float) – Absolute metallicity of gas in the hosting galaxy.

  • Zi (float) – Average atomic number of gas in the hosting galaxy.

Return type:

None

gff(il=None, Te=None)

Computes the Gaunt Factor as given in Draine, 2011 (Eq.10.9):

\[g_\text{NFF}=\ln\left\{\exp\left[5.96-\frac{\sqrt{3}}{\pi}\, \ln\left( Z_i\, \frac{\nu_\lambda}{G\text{Hz}}\, \left(\frac{T_e}{10^4\, K}\right)^{-1.5}\right)\right]+ \exp(1)\right\}\]

where \(T_e\) is the electron temperature (function argument), \(Z_i\) the average atomic number (class parameter) and \(\nu_\lambda\) is the frequency at given wavelength (\(\lambda\) as defined in the grid used to instantiate the class)

Parameters:

  • il (1d array or scalar integer) – indices in the instance wavelength grid. If None, the gaunt factor is computed over all the wavelength grid.

  • Te (float) – electron temperature of the medium, if None, the internal function NFF.Te() is used.

Returns:

Gaunt Factor at given wavelength

Return type:

1d array or scalar float

Te(Zgas=None)

Electron temperature as empirically derived in Vega et al., 2008:

\[T_e = \exp\left\{3.89-0.4802\, \log(Z_\text{gas}/0.02)-0.0205\,[\log(Z_\text{gas}/0.02)]^2\right\}\]

where \(Z_\text{gas}\) is the absolute gas metallicity.

Parameters:

Zgas (float) – (optional, default = same as parameters set) the average absolute metallicity of the gas. If None, it will use the internally stored parameter (can be set with NFF.set_parameters( Zgas = ... ))

Returns:

Electron temperature at given metallicity

Return type:

float

emission(Q_H, il=None)

Intrinsic Free-free emission as given in Draine, 2011 (Chapter 10):

\[L_\text{NFF}(\lambda,\tau) \approx 1.8\times 10^{-27}\, \text{erg}\,s^{-1} \text{Hz}^{-1}\cdot \dfrac{\mathcal{Q}_\text{H}(\tau)}{s^{-1}}\, \left(\dfrac{T_e}{10^4\, K}\right)^{0.3}\, g_\text{NFF}\, \exp\left(\dfrac{-h_P\, \nu_\lambda}{k_B\, T_e}\right)\]
Parameters:

  • Q_H (float) –

    intrinsic photo-ionisation rate, can be computed from the intrinsic stellar luminosity:

    \[\mathcal{Q}_\text{H}(\tau) = \int_0^{912\mathring{A}}\text{d}\lambda\, \frac{L_\text{CSP}^\text{i}(\lambda,\tau)}{h_P\, \nu_\lambda}\]

    where \(h_P\) is the Planck constant and \(\nu_\lambda\) is the frequency at given wavelength \(\lambda\). The intrinsic stellar luminosity, \(L_\text{CSP}^\text{i}(\lambda,\tau)\), can be computed using function galapy.CompositeStellarPopulation.CSP.emission().

  • il (1d array or scalar integer) – indices in the instance wavelength grid. If None, the emission is computed over all the wavelength grid.

Returns:

intrinsic emission due to Free-Free transitions.

Return type:

1d array or scalar float