wCDM

class astropy.cosmology.core.wCDM(H0, Om0, Ode0, w0=-1.0, Tcmb0=2.725, Neff=3.04, name='wCDM')[source] [edit on github]

Bases: astropy.cosmology.core.FLRW

FLRW cosmology with a constant dark energy equation of state and curvature.

This has one additional attribute beyond those of FLRW.

Examples

>>> from astro.cosmology import wCDM
>>> cosmo = wCDM(H0=70, Om0=0.3, Ode0=0.7, w0=-0.9)

The comoving distance in Mpc at redshift z:

>>> dc = cosmo.comoving_distance(z)

Attributes Summary

w0 Dark energy equation of state

Methods Summary

de_density_scale(z) Evaluates the redshift dependence of the dark energy density.
efunc(z) Function used to calculate H(z), the Hubble parameter.
inv_efunc(z) Function used to calculate \frac{1}{H_z}.
w(z) Returns dark energy equation of state at redshift z.

Attributes Documentation

w0[source]

Dark energy equation of state

Methods Documentation

de_density_scale(z)[source] [edit on github]

Evaluates the redshift dependence of the dark energy density.

Parameters :

z : array_like

Input redshifts.

Returns :

I : ndarray, or float if input scalar

The scaling of the energy density of dark energy with redshift.

Notes

The scaling factor, I, is defined by \rho(z) = \rho_0 I, and in this case is given by I = \left(1 + z\right)^{3\left(1 + w_0\right)}

efunc(z)[source] [edit on github]

Function used to calculate H(z), the Hubble parameter.

Parameters :

z : array_like

Input redshifts.

Returns :

E : ndarray, or float if input scalar

The redshift scaling of the Hubble consant.

Notes

The return value, E, is defined such that H(z) = H_0 E.

inv_efunc(z)[source] [edit on github]

Function used to calculate \frac{1}{H_z}.

Parameters :

z : array_like

Input redshifts.

Returns :

E : ndarray, or float if input scalar

The inverse redshift scaling of the Hubble constant.

Notes

The return value, E, is defined such that H_z = H_0 / E.

w(z)[source] [edit on github]

Returns dark energy equation of state at redshift z.

Parameters :

z : array_like

Input redshifts.

Returns :

w : ndarray, or float if input scalar

The dark energy equation of state

Notes

The dark energy equation of state is defined as w(z) = P(z)/\rho(z), where P(z) is the pressure at redshift z and \rho(z) is the density at redshift z, both in units where c=1. Here this is w(z) = w_0.

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