wCDM¶

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

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

`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`.
`de_density_scale`(z)	Evaluates the redshift dependence of the dark energy density.

Attributes Documentation

w0[source]¶: Dark energy equation of state

Methods Documentation

efunc(z) [edit on github][source]¶

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) [edit on github][source]¶

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) [edit on github][source]¶

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 $w(z) = w_0$ .